course session 306012 introduction to storage networks

8/6/2019 Course Session 306012 Introduction to Storage Networks

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ntroduction to storage networksFlexible and redundant storage can solve many network problems, and storage area networks (SANs)

rovide the solution. In this class, you'll learn the range of current storage issues and settings and

dentify areas that provide tangible returns for an investment in storage networks. Along the way, you'llearn about SAN disks, host bus adapters, switches and management tools.

Lessons

Is a storage area network right for your organization?1.

In this first lesson, you'll learn the role of storage network solutions in adapting

your organization's network from a patchwork quilt of single-purpose servers to

an interwoven fabric of storage resources.

Exploring virtual storage2.

In this lesson, you learn what virtual storage is and discover its benefits. You

also learn how using an all-in-one solution can help you get started quickly and

easily and review migration and upgrade paths for moving your data.Understanding SAN disk solutions3.

In this lesson, you'll delve into the technologies behind SANs. You'll learn about

data protection with redundant drives and data backup, as well as performance

implications in designing a SAN.

Discovering SAN controllers, cables and connectors4.

SANs are made up of two main components: storage devices, in the form of

disk and tape drives, and networking components, which include adapters,

cables and switches. In this lesson, you learn about the networking components

of a SAN.

Exploring topologies and switches5.

This lesson focuses on ways to interconnect storage network components.

You'll learn about topologies and the role of switches and the services theyprovide. You'll also delve into more detail on the switches that tie a SAN

together.

Managing and administering SAN software6.

SAN systems require management to keep them running smoothly. This lesson

covers using management software, zones, policy-based tools and LUN

masking to ensure your SAN is secure and functioning efficiently.

s a storage area network right for your organization?n this first lesson, you'll learn the role of storage network solutions in adapting your organization's network from

patchwork quilt of single-purpose servers to an interwoven fabric of storage resources.

Welcome to Introduction to storage area networks

Welcome to Introduction to storage networks. Storage of your organization's data is critical to its business

perations. Every day, users access, modify and share data that enables the organization to function.

However, data storage can quickly become unmanageable when storage capacity must increase to

ccommodate the vast quantities of information created daily and stored for months or years. This class

xplains how to investigate your organization's storage needs and evaluate storage technologies to

etermine which best fits your requirements.

This class is geared toward IT personnel who are responsible for network storage planning for small

and medium-size businesses (SMBs).

One solution to meeting data storage needs is using a storage area network (SAN)—a centrally

onsolidated, virtual disk storage system that's separate from network traffic and shared by servers.



What you'll learn

The lessons in this class are designed to build on one another and give you practical information to help

ou make informed decisions when planning your network storage. Here's what the lessons cover:

Lesson 1: Is a storage area network right for your organization? covers options in storage

technologies, explains how SANs can benefit your organization and gives you an overview of

assessing your current and future storage needs.

Lesson 2: Exploring virtual storage answers the question "What is virtual storage?" You delve into the

components and capabilities of the SAN infrastructure, including virtualizing and migrating your data.

Lesson 3: Understanding SAN disk solutions explains how you can use SAN disk components to set

up virtual storage solutions while considering performance and redundancy factors.

Lesson 4: Discovering SAN controllers, cables and connectors covers the network

components—controllers, cables and connection technologies—that enable SANs to move data from

disk to server.

Lesson 5: Exploring topologies and switches describes the SAN switch protocol for interconnecting

servers and disk arrays, which provides the expansion and management capabilities that make a SAN

infrastructure such a huge advantage for your organization.

Lesson 6: Managing and administering SAN software covers storage area network management and

describes techniques for administering your SAN, such as using device zones and SAN utilities.

Each lesson includes an assignment to help you to apply the concepts to your organization as well as a

hort quiz to check your comprehension of the topics.

After completing this class, you'll have a wealth of information available to understand how a SAN can

rovide your organization with the data storage and management tools it needs to efficiently provision

ost-effective storage resources.

Now that you have an overview of what this class offers, it's time to get started with your first lesson.

Traditional data storage options

The amount of data an organization must store isn't always related to the organization's size and data

torage needs can change rapidly. For example, when an organization adds new products or services,

ften its client database grows faster than planned.

Just because your organization is small doesn't mean your data storage requirements are small.

So how can an organization keep up with the need for more storage? These are the traditional storage

echnologies that have been used to solve this problem:

Direct attached storage

Network attached storage

The following sections discuss the advantages and disadvantages of each technology. To see them

ummarized and compared with SAN technology in an at-a-glance table, refer to the section on SANs

ater in this lesson.

Direct attached storage

Any storage that's physically connected to a single host machine can be considered a direct attached

torage (DAS) system. The hard disk in a desktop computer or server is a simple example. DAS

echnology is fast because the storage system is dedicated to one host.

DAS systems can be made up of internal or external drives, which are an economical way to add storage.

nternal drives include several technologies such as small computer storage interface (SCSI), parallel

ATA (PATA) which is often times referred to as integrated drive electronics (IDE) and serial ATA (SATA).

External drives typically use the same physical hardware as the internal drives, but add electronics to



nable them to be used through an external interface. Examples of these interfaces include universal

erial bus (USB), FireWire and external serial ATA (eSATA).

Although these drives are economical, they're limited to providing storage for the system to which they're

ttached. Therefore, expansion is more difficult than with other storage solutions. An alternative—network

ttached storage—enables any server on the network to use storage.

Network attached storage

Servers have a way of multiplying in an organization. You might add one for email and another as a

hared application server for several departments. Before you know it, you have many servers handling

mportant tasks, and each one requires separate storage. If you continue using a DAS system, your

rganization might end up purchasing a lot more storage than it needs. For this reason, shared storage

echnology can be of value.

A storage system that shares network bandwidth with standard server and user traffic is called network

ttached storage (NAS). Devices called NAS appliances share data over the network without adding

multipurpose server software, which can be expensive and difficult to maintain. NAS systems are easy to

perate and maintain and allow modest expansion. The hardware is usually affordable and provides

ome management functions along with the sharing capability.

NAS systems are subject to limitations of the underlying network's speed in accessing data. For example,

Fast Ethernet local area network (LAN) has a theoretical data transfer speed of 12.5 Mbps (megabytes

er second). The actual speed of accessing data drops, however, when NAS appliances are using the

etwork's bandwidth. Factor in network bandwidth for activities such as web surfing, printing and email

nd the available data rate for storage decreases even more.

What can an organization do to expand its storage so that it can be shared by servers yet have enough

peed to be effective? SANs were developed for just this purpose, as you learn in the next section.

Realizing the benefits of a SAN

As mentioned, many networks are set up on a one-application, one-server basis with separate servers for

ach organizational function or department. With separate storage for each server, sharing data and

esources is difficult and can slow network performance. As you add more servers, management can

ecome time consuming, too.

n a SAN system, all those separate storage disks are grouped and consolidated in an array. Servers can

hen access the array as though it were a local storage device. This setup also provides a separate

etwork that's used only for transferring data between storage systems and servers. This network is

ptimized for fast data transfer at speeds of 2 to 10 Gbps (gigabits per second).

SANs are made up of several components, such as disk arrays and switches, as you'll learn in

Lessons 2 and 3.

SAN components connect servers and storage in what's known as a SAN fabric. Figure 1-1 shows a

ypical SAN fabric.

No doubt, the term "fabric" was coined because storage and servers are interconnected with strands

of fiber optic cables. These fibers are then woven into a fabric of connectivity.



Figure 1-1: A SAN fabric is made up of many interconnected fiber optic strands.

Enlarge image

In many computer networks, workstations and servers have a single connection to the network, but a

SAN fabric has multiple connections.

Redundant connectivity reduces downtime for users, which is important to ensuring high availability for

ata and network resources. A SAN's separate, centralized setup also reduces downtime and offers the

ollowing benefits:

Reduces the space required for a one-application, one-server setup

Eases the burden of management tasks, including backups and recovery

Reduces the incremental costs associated with adding storage

Increases the visibility into planning for storage growth as an organization

Improves security by separating storage processes from normal network traffic

An important concept of SANs is the "virtualization" of data storage. Because storage is centralized as a

irtual pool of resources, you can allocate storage to servers as needed quickly and easily. With recent

egulations mandating that some industries, such as health care, retain data for longer periods, manyrganizations are facing rapidly expanding storage requirements. Virtual disk storage makes handling this

storage explosion" easier.

To understand the benefits a SAN can have for your organization, comparing the strengths and

weaknesses of DAS and NAS systems with SAN technology is helpful. Table 1-1 compares the basic

eatures of each technology.

Storage

feature

DAS NAS SAN

Storage

capacity

Limited to ports on the local

server

Not limited Not limited

Speed of

accessing

storage

Fast Somewhat slow Very fast

Ease of

adding

storage

Might require shutting

down servers to add

storage

Easy Easy

Redundant

connectivity

No No Yes

Centralized

management

No No Yes

Ease of expansion Limited to host's physicalports Allows modest expansion Quick and easy

Suited for

databases

Yes No Yes

Suited for file

storage

Yes Yes Yes

Cost Inexpensive Moderately expensive Moderately expensive

http://h30187.www3.hp.com/media/ns/11187/HPSMB_SAN01fg01_large.jpg



Distance

between

server and

storage

Must be close (under 6

feet)

Up to hundreds of miles Up to hundreds of miles

Backups Each volume copied

separately from server to

tape

Each volume copied

separately from server to

tape

Can back up multiple volumes

without server interaction

Table 1-1: Comparing storage technologies.

Because SAN technology offers different advantages from an NAS or DAS system, you might want toreate a hybrid system incorporating each of these technologies. For example, a developer's server that's

sed to test new changes to a production application may need to be a very low cost implementation with

ttle consideration for performance. This type of server may use very low cost DAS to support a small

esting database. Production servers supporting the same application will no doubt support more users

nd require the performance and scalability that a SAN provides. To help you make that decision, assess

he importance of the following factors as you compare the features in Table 1-1:

Performance

Availability

Scalability

Cost

As you can see, SANs offer a fast, flexible method for connecting consolidated storage to the servers in

our organization. By efficiently allocating storage resources as they're needed, your organization will

ave both time and money by reducing the overspending on unmanaged DAS or NAS storage resources.

As you delve into the technical details of SANs in upcoming lessons, these benefits will be even more

pparent.

Now that you've seen what SANs can offer your organization, continue reading to learn how to assess

our current environment to determine whether a SAN solution is right for you.

Taking inventory and assessing your storage needs

To understand how your organization can benefit from using SAN technology, you need to take inventory

f the storage you currently use and get a handle on your projected future needs. Getting an accurate

iew of your organization's overall storage picture can be daunting, especially if each department has its

wn standalone storage. If your organization has been adding storage over a long period for different

unctions—an email server one year and a database server the next year, for example—this task can be

ven more challenging.

Although taking an inventory of this type of "server sprawl" setup can be time consuming, the results can

elp you present a compelling case for using a SAN. For example, scattering storage all over the network

nevitably means duplication of IT management efforts. Upper management usually responds favorably to

he potential for a good return on an investment (ROI) in SANs if you can show a reduction in the

verhead of having several IT staff performing the same management tasks.

Although advantages such as redundant connectivity and more efficient backups are clear benefits of

SAN vs. DAS and NAS to those working directly with the network, upper management might not view

these advantages with the same weight as factors offering a clear-cut ROI, such as allowing the staff

to do more in less time and efficiently allocating storage using centralized management tools.

The assignment for this lesson explains in more detail how to create an inventory of your current storage

equirements. In general, you want to collect information such as the following:

Storage devices, including type (DAS or NAS, for example), capacity and location

Host machines

Connection devices, such as switches and bridges

Any distance considerations—for example, LANs in branch offices

Applications, including performance and availability requirements



n addition, review your past growth in storage requirements to estimate how much your storage capacity

eeds might increase in the next year. The goal is to make sure your storage solution can handle future

xpansion without unnecessary downtime and management headaches as well as to keep the costs from

piraling out of control.

n upcoming lessons, you delve into the nuts and bolts of SAN technology and learn more about disk

rives, SAN switches and network cards, external cabling and software management tools.

Moving on

n this lesson, you reviewed traditional data storage options and learned that SANs combine flexibility with

igh-speed connectivity and consolidate your organization's storage in a centralized virtual storage pool.

n Lesson 2, you learn more about SAN features and options for building a high-performance SAN to

ncrease your data storage sensibly. Before you move on, complete the assignment and take the quiz for

his lesson. See you there!

Assignment #1

Your assignment for this lesson is to make an inventory of your organization's current data storage.This task might sound easy, but even small organizations often have data spread over many storage

evices, such as USB drives, server hard disks and NAS systems. Collect the following information,

triving for as much detail as possible. You might find it helpful to put your information in a

preadsheet for easy reference.

List all storage devices (with make and model) used in your organization. Include each device's

storage capacity (used space and free space), type of storage (DAS, NAS and so on), type of

connection it supports and location.

List the total number of host machines (workstations, servers and so on). For each host, include the

operating system (OS), type of connection it supports and applications running on it.

List all connection devices, such as switches and bridges, including their type and connection

speed.

List any distance considerations, such as LANs in branch offices that require storage.

List all applications your organization uses with their current storage requirements. Include

performance and availability requirements for users. You might also want to specify traffic patterns

for applications, such as peak periods of use.

Calculate the total amount of storage your organization uses.

After assessing the current state of your storage situation, projecting future storage needs and

nderstanding how a SAN can improve your data management are easier.

Quiz #1Question 1:

How does a SAN differ from an NAS system?

A) SANs use only fiber optics.

B) SAN and NAS are different acronyms for the same thing.

C) Network activity on a SAN is separate from other server and user traffic.

D) Network activity on an NAS system is separate from other server and user traffic.

Question 2:

Which of the following is a compelling advantage you can use to convince upper management that a SAN's

onsolidated storage is the best option?

A) Reducing duplication of IT management's time and effortsB) Using current network bandwidth for storage processing

C) Reducing space requirements

D) Increasing data backup speed

Question 3:



True or False: An NAS system is faster than a DAS system because it uses the underlying network's data

ransfer rate.

) True

B) False

Question 4:

What advantages can a SAN offer over DAS and NAS solutions? (Check all that apply.)

A) Lowest cost

B) Centralized management

C) Reduced downtime

D) Fast data transfer speeds

Question 5:

Which of the following storage solutions is the most difficult to expand?

A) Storage area networks

B) Network attached storage

C) Server-based storage

D) Direct attached storage

Exploring virtual storagen this lesson, you learn what virtual storage is and discover its benefits. You also learn how using an all-in-one

olution can help you get started quickly and easily and review migration and upgrade paths for moving your

ata.

Understanding virtual storage

Welcome back! In Lesson 1, you reviewed the storage technologies organizations often use, compared

hem with SAN technology to see the flexibility and efficiency SAN offers. We covered how, when

ompared with DAS and NAS technologies, SAN provided:

Unlimited storage provisioning

Superior management of consolidated storage

Higher performance

You also learned the importance of doing a thorough inventory and assessment of your current and future

torage needs. As you work through this lesson, keep your Lesson 1 assignment handy. You can refer to

his inventory of your current storage as you learn about SAN storage capabilities in this lesson.

Storage consolidation

Storage consolidation is a major benefit of using SANs. With consolidation, you can manage separaterives and drive array storage units as part of a larger pool. As you learned in Lesson 1, storage

echnologies are based on the building block of a single physical drive. Adding drives requires some sort of

onnectivity and power to make it possible to use the storage. By consolidating these connections within a

torage unit, drive connections are made using an internal wiring harness that both eliminates clutter, but

more importantly, allows each drive to be replaced independently should it fail.

Lesson 3 explains the details of how physical drives are connected in a SAN.

Each physical drive added to a server or storage unit, as shown in Figure 2-1, requires separate power

nd connectivity cabling to make it work. As storage units are filled with drives, more storage units must bedded. Each storage unit also requires some kind of connectivity so that the drives in the unit can transfer

ata to and from systems using that storage.



Figure 2-1: Drives are aggregated into storage units.

Building blocks of storage

This growing collection of drives housed in multiple cabinets (storage units) isn't useful without a way to

manage all the raw storage, however. Management is where the power of SAN technology starts to shine.

With SAN technology, the storage space on each drive is divided logically into storage blocks, as shown in

Figure 2-2, that can be assigned as a larger group spanning multiple physical drives.

Figure 2-2: Logical storage blocks on a physical drive.

Enlarge image

These storage blocks are managed as a single virtual storage device called a storage pool. Managingtorage as a pool makes it possible to allocate a portion of the storage to individual servers that are

onnected to the consolidated storage on the SAN. For example, when a server requires storage space,

ou can assign it as a group of storage blocks that might span many different physical drives in that

torage pool. Virtual storage hides the underlying physical infrastructure's complexity so that you can

llocate storage to meet servers' needs more easily.

By abstracting the way a server sees storage from the way drives actually read and write it, the

possibilities for adding, moving and copying storage become interesting, as you see later in this

lesson.

Volume allocation

As shown in Figure 2-3, physical drives have a number of storage blocks allocated to provide servers with

olumes used to store data. These volumes are allocated storage blocks based on a server's needs, as

hown in Figure 2-3.




Figure 2-3: Storage blocks are allocated to server volumes.

Enlarge image

As you can see in Figure 2-3, not all storage blocks on a drive are allocated to a server volume. The

nallocated storage blocks are expansion space that can be assigned to a volume on another existing

erver or a new server that's added later.

Storage use

Determining storage allocation amounts is still more of an art than a science. Although you can estimate

torage use fairly accurately for current applications, determining how new applications, new regulations or

usiness growth can affect storage allocation is often difficult. In your Lesson 1 assignment, you reviewed

he storage allocated to servers in your current environment. You might have noticed the following trends:

Some servers were using almost all the storage attached to them.

Some servers had a lot of unused storage.

Some servers had more than one type of storage technology (for example, DAS and NAS).

These trends point out the difficulty of allocating storage efficiently with traditional storage solutions. That's

why many organizations continue purchasing new storage every year, even though they have quite a bit of

nused storage. For these organizations, SAN's flexibility and efficiency in allocating storage can

ontribute to a positive ROI.

Allocating storage efficiently in your organization can save tens of thousands of dollars every year, not just

n the cost of purchasing new storage devices, but in the management and installation time needed to add

torage.

Now that you understand the rationale of virtual storage, continue reading to learn ways you can

ncorporate this technology into your organization.

Discovering an all-in-one solution

Some organizations, locations may not have employees dedicated to storage management. Even large

rganizations might not have IT professionals who are knowledgeable about using SAN technology. Also,

n the past, switching to SAN technology has meant a sudden costly investment in new hardware and

oftware. You learn more about management software in Lesson 6, but for now, it's helpful to know that

olutions are available that enable IT professionals to manage storage like a expert and make it possible

or organizations to move to a SAN without a huge initial investment.

The task of allocating storage to server volumes from a consolidated storage pool can be daunting if you

on't have a solution designed to walk you through the steps and enable you to manage storage easily.

uckily, a few vendors have entry-level products called all-in-one solutions that you can use to capitalize

n the benefits of SAN technology.




Look for vendors that offer both all-in-one and enterprise-level storage solutions. All-in-one products

often incorporate the expertise used to develop the more expensive enterprise-level products in a

vendor's line but at a lower cost and with more simplified management tools.

By using an all-in-one solution that combines hardware and software, you can do the following more

asily:

Consolidate your storage.

Reduce your data center space requirements.

Reduce expenditures on extra storage.

Manage the storage your organization already owns more efficiently.

n addition, most all-in-one solutions have quick-start guides and data migration utilities so that you can

tart using new storage solutions in your current environment quickly and easily. After all, you want to

migrate your data to a new, more manageable storage platform as soon as possible.

Don't dismiss all-in-one SAN products as lightweight alternatives to the "real thing." Many all-in-one

roducts have more features than your current solution.

Many all-in-one SAN products allow you to integrate your new storage into the current environment by

everaging the infrastructure that exists within your current network. For example, advanced SAN

nstallations require multiple switches, fiber-optic cabling and training to maintain the new infrastructure.All-in-one solutions allow you to connect to your existing LAN switching gear with standard copper wiring

nd offer integrated electronics to manage new drives in the storage unit. We'll cover some of these

onnection details in Lesson 3 as we go over the connectivity options that are available when setting up a

SAN system.

All-in-one solutions are an easy way to get started with SANs. What do you do, however, when you

utgrow your all-in-one solution's capacity?

Understanding migration and upgrade paths

Storage growth is inevitable in organizations. As you've seen in this lesson, virtual storage allows

llocating storage blocks to servers as needed and allocating unused storage to new servers you've

dded. However, at some point, you'll run out of storage. What options do you have?

At some point, your organization will need to add storage, and SAN technology can make that process

easier.

Adding storage

One option is simply adding more physical drives to your current setup. With a SAN's block-level

llocations, this option is easier than with other storage technologies. New drives become part of the

irtual storage device, and their storage blocks can be allocated as needed. When new storage is needed

y expanding server volumes, it can come from many different drives in the SAN infrastructure. To make

his process even easier, SAN management software controls how server volumes use storage blocks

ehind the scenes. SAN technology ensures that increasing storage by adding physical drives is done as

fficiently as possible so that you don't purchase more drives than you actually need.

Migrating storage

Another option is purchasing a new storage solution and moving your current data to it. As with any

echnology, newer, faster or less expensive storage solutions that your organization wants to take

dvantage of will become available, or perhaps your organization has outgrown the capacity of the all-in-

ne solution you started with. When you purchase new SAN hardware, you need a way to move data on

our current SAN infrastructure to the new hardware.



This migration can take place seamlessly, depending on how advanced the software is. Because of the

bstraction of physical drives and the virtual storage allocated to server volumes, migrating data from one

SAN device to another can be done by using block-level copying. Figure 2-4 shows the concept of block-

evel copying. Each block within the storage device is copied by the SAN, rather than by the server that

may be assigned that particular storage block, to another storage unit. As long as the server and

pplications using data can access the virtual storage device, it doesn't matter where data is stored

hysically.

Figure 2-4: Migrating data with block-level copying.

Enlarge image

After storage is copied from one device to another at the block level, the virtual storage device remaps

where data is located so that servers can start to take advantage of the new SAN infrastructure

mmediately. Block-level copying reduces downtime and increases flexibility, particularly for disaster

ecovery procedures, as you'll learn in Lesson 5 when we discuss SAN topologies.

Server volumes are allocated on the virtual storage device, so the underlying physical drives can be

managed without affecting the way the server sees its data.

With SAN management software, you can view your storage network as a single entity, which makes it

asier to configure and monitor storage components during a data migration.

Moving on

n this lesson, you learned how physical drives are divided logically into storage blocks that are allocated

o server volumes. You have also seen how to use virtual storage to manage adding drives and migrating

ata without affecting the servers using that storage. In Lesson 3, you learn more about disk drive

echnology to understand how data is protected and how to improve storage performance with fiber optics.

Before you move on, complete the assignment and take the quiz for this lesson.

Assignment #2

For this assignment, assess the following for your current environment:

Determine which servers in your network have the most storage space.1.

List which servers have shown the most increase in storage growth over the2.

past year.

Note the age of all your current storage devices.3.

These assessments will be helpful when you start to evaluate the process of building

our organization's SAN solution.

Quiz #2Question 1:

True or False: Servers connected to a SAN can use only specific physical drives for storage.




Data backups

Archives

Temporary storage

Even within these broad storage categories, there can be varying levels of importance. For example, your

rganization might value a customer database more than a database of parking assignments at the main

ffice. Both are databases, but they have different levels of importance. You use this information to

etermine how to allocate storage in a SAN.

To plan a SAN successfully, know your data and understand its importance to your organization's

operations.

While reviewing the types of storage your organization depends on, ask the following questions to help you

etermine the options you have:

How can an important database achieve the best performance?

How can archival file storage be cost effectively allocated?

What options are available to prevent data loss if a drive fails?

To answer these questions, you'll need to understand the disk components that determine data storage

peed and expense, which is the topic of the next section.

mproving performance with disk components

As you learned in Lesson 2, the basic building block of SAN storage is physical drives. Not all drives are

he same, however. These factors determine how fast data can be read to or written from a drive:

Number of platters and heads

Data density on each platter

Platter rotational speed

Bandwidth of the drive's connection

An increase in any of these factors can improve performance but also increase costs. Therefore, ranking

he importance of your data storage is important to make sure your storage solution is cost effective. Your

rganization might decide to spend more on fast data storage for critical applications but be unwilling to

pend much for data of lesser importance.

Platters and heads

Each drive contains aluminum or glass platters with a thin magnetic coating that stores data. The number

f platters in a drive determines the drive's physical size, capacity (amount of data it can store) and how

much data can be transferred in and out. Heads are mechanisms that transfer data to or from the platters;

hey're sometimes called "read/write heads." Typically, drives have two heads for each platter—one for ach side of the platter.

n drives with more platters, more data can be read with each platter rotation (pass). For example, a drive

with two platters has four heads that can read or write a certain amount of data with each pass. However, a

rive with four platters has eight heads that can read or write twice as much information with each pass.

Data might not be read simultaneously with each head, or the next data might not be positioned where

any heads are located, thus requiring the head to move to another location during subsequent rotations

to get to data.

Data density

The amount of data a platter can store depends on the technology used. As the chemicals used to create

his layer improve and heads can read data in smaller areas, the amount of data you can store in the same

mount of space can increase. Because there are two main physical drive sizes, 3.5 inch and 5 inch,



ncreasing the density of data stored on a platter is essential for getting large-capacity drives.

Although higher densities allow for larger capacities, the technology might not always translate to faster

performance.

Platter rotational speed

nside each drive, a motor spins the platter, allowing the heads to float over the platter's surface and read

he data on it. As platter speed increases, so does the drive's power consumption, heat output and noise.

This added speed reduces the time needed to make an entire rotation, however. If data is read on one

ass before the head moves to another area to read the next set of data, it happens more quickly with a

aster rotational speed. The following table shows different uses for platter speeds in rotations per minute

rpm).

Platter rotational speed Typical use

7,200 rpm File storage, inexpensive server storage

10,000 rpm Mid-range database storage, streaming video storage

15,000 rpm High-use database storage, high-definition video editing storage

Table 3-1: Typical uses of platter rotational speeds.

You might think that using the fastest drive available is the best option, but keep in mind that the faster the

latter rotational speed, the more expensive the drive is. For a database that doesn't get much use, for

xample, buying a 15,000 rpm drive isn't cost effective. You'll have more speed than you need, and power

onsumption, heat output and noise will be higher than necessary.

Connectivity bandwidth

esson 1 covered connectivity types for drives (SCSI, ATA, serial ATA and USB). These connectivity

ptions enable data to be streamed from the drive to applications that need it. Some options are faster thanthers, which allow drive heads to pump data from the platter continuously. As you might imagine, the

andwidth of these connections can affect data flow if the heads can read more data than the connection

an transfer. If the connectivity cannot stream the data as fast as it's read from the drive, the drive will

uffer some of the data temporarily in a small on-board memory chip. However, once the RAM buffer

apacity is reached, the drive will wait to read more data. This increases the potential delay as the platter

pins and the data that would have been read moves farther out of position until the full rotation finally

rings it back around to the head's position.

Considering your RAID configuration

You've been concentrating on the performance of data streaming from drives, but you should also consider

ow to protect data stored on drives. Component failures are inevitable, so planning for these failures is

ssential. The primary mechanism for managing data replication in a SAN is a redundant array of

nexpensive drives (RAID) system. The following table describes the available RAID levels.

RAID

evel

Description

RAID

0

Creates data "stripes" across multiple drives, which makes it possible to read data more quickly than

on a single drive but doesn't protect data if any drive fails.

RAID

1

Creates a mirrored drive set, in which data is written to two duplicate drives simultaneously. If one

drive in the mirrored set fails, the other drive can still operate and store all the data.

RAID

3

Creates a striped data set similar to RAID 0 but includes an extra drive containing additional

information called parity data. With this feature, if one drive in the set fails, lost data can be re-

created so that the drive set can continue operating.

RAID

5

Similar to RAID 3, but parity data is striped across the entire group of drives instead of being stored

on one dedicated drive. Therefore, every drive can manage a portion of the drive set's parity data.

RAID

10

In this combination of RAID 1 and RAID 0, data is striped across a set of drives and then mirrored to

another set of drives. This type of mirroring removes the extra step of calculating parity data every



time data is written to the drive.

Table 3-2: RAID levels.

A SAN system can usually support every RAID level, so you can configure a RAID level based on the

torage allocated to the server. Some factors that help you determine the right RAID level include the

ollowing:

Tolerance for delays in writing to the drive

Performance effects during the RAID rebuilding phase

Tolerance for the RAID rebuilding process when a drive fails

Tolerance for writing delays

When data is written to a RAID system, the RAID software (whether on a chip or in firmware on the

ontroller) must calculate parity data before data is written to drives in the set. This calculation is usually

apid but still requires time. RAID 5 works for most applications; however, if the SAN volume using RAID

as a lot of activity, application performance might be affected. In this case, consider using RAID 1

mirroring) to eliminate the overhead of parity calculations. Just remember that you'll spend twice as much

n storage because every drive has a mirrored duplicate drive.

Performance effects during RAID rebuilding

When a drive in the RAID set fails, every operation must undergo a RAID parity calculation to make up for

he drive that failed. This process reduces the RAID system's overall read performance. Additionally, when

new drive is installed to replace the old drive, every byte of data on the volume must be recalculated and

opied to the new drive. During this operation, the RAID system's performance degrades.

Tolerance for RAID rebuilding when a drive fails

Most RAID hardware monitors idle periods to reduce the impact of the rebuilding process, at the cost of

aking longer to rebuild data. During rebuilding, therefore, data is at risk of a secondary failure. RAID 1mirroring) has a similar rebuilding process, but read performance isn't affected as much because there's

o need to recalculate parity data. However, managing a mirrored set requires twice as much storage.

Remember that RAID levels above 0 (simple striping) always require more drive space to protect your

data. This drive space costs more but adds redundancy to your SAN for data protection.

These factors, weighed against the costs and survivability requirements you have for certain types of data,

elp you determine which RAID level to use. You have other options for storing backups of your data,

owever, that don't involve using drives. The next section discusses non-disk storage options.

Backing up data with non-disk storage

Storing data on a SAN has an often overlooked advantage. When you store data on traditional DAS

ystems, the server needs to spend cycles reading the data to back it up to a local or networked drive. So

uring backup operations, the server's performance is reduced, and the load on the local area network

LAN) increases. The time a backup operation takes is called the backup window. The more data a server

as, the longer the backup window is. As you continue adding storage, the backup window might be longer

han the "off hours" you've allotted for backups (usually nights or weekends). When the backup window

pills over into normal work hours, the performance of an organization's day-to-day operations is affected.

Organizations use three basic types of backups:

Full backup: All data on the volume is copied.

Differential backup: All data that has changed since the last full backup is copied.

Incremental backup: All data that has changed since the last incremental backup is copied.



The following table summarizes each backup type's advantages and disadvantages.

Backup

type

Advantage Disadvantage

Full

backup

All data is copied, so you have a complete set of data if recovery is

required.

Takes the

longest to

complete and

requires the

most storage

because all data

is being copied.

Differential

backup

This type is a good compromise between full and incremental backups. It

requires less storage and takes less time than a full backup, and fewer data

sets are needed to restore the volume to the last full backup than with

incremental backups.

As the time from

the last full

backup

increases and

more files are

modified,

backups take

longer and

require more

storage.

ncremental

backup

This type is the fastest and requires the least amount of space because

only data that has changed since the last incremental backup is copied.

If recovery is

needed, this

method requires

restoring the

most data sets.

The full backup

plus every

incremental

backup since

the full backup

are needed to

restore the

current volume.

Table 3-3: Backup types.

Because a SAN maps storage into virtual volumes and assigns them to separate servers, it maintains

ontrol over all storage components. Most SANs include a tape system for reading data directly from the

SAN instead of through each server. This backup advantage reduces the amount involvement that the

ervers themselves as well as eliminating the LAN traffic.

For example, if your organization has five servers, with 100 GB of data allocated to each, the SAN-

ttached tape system can access all 500 GB of data through the SAN, instead of pulling data from each

erver. During a tape backup, the SAN can be instructed to create a snapshot, in which all data at a point

n time is "frozen." During a snapshot backup, the SAN maintains any changes that would normally be

pplied to the file in a way that the data is actually written to after the backup of the file is completed.Unless a file is extremely large, the backup will usually complete without requiring a large number of

elayed writes. Figure 3-1 illustrates this process.



Figure 3-1: SAN snapshots used to back up live data.

Enlarge image

With a SAN-attached tape system, the servers and the LAN aren't affected during backup operations.

Backups can take place during working hours without affecting servers that handle user requests, and

etwork performance isn't reduced when huge amounts of backup data are streaming over the LAN.

Additionally, backup operations are homogeneous, so you don't have to manage different platforms for

ackup software and tape systems.

By consolidating the backups done over the SAN, the management time saved in just backup operations

ould save thousands of dollars per year in time spent swapping tapes and checking logs from multiple

ystems within an organization with less than a dozen servers.

Moving on

Now that you've seen how your organization can benefit from the disk storage features a SAN can offer

nd know how to protect your data from failures, in Lesson 4 you move on to explore the hardware used to

reate a SAN and connect your servers to a pool of managed storage. Before you move on, do the

ssignment and take the quiz for this lesson. See you there!

Assignment #3

Review the importance of data on current servers in your network, and then assign a RAID level

o each volume based on what you learned in Lesson 3. Using this list of volumes and associated

RAID levels, re-calculate your storage needs based on the following formulas:

RAID 0: You shouldn't be considering RAID 0 because it affords no data protection.

RAID 1: Double your current storage space to determine the total amount of storage required.

RAID 3: Multiply your current storage by 115 percent to include space for a RAID parity drive.

RAID 5: Multiply your current storage by 115 percent to include space for a RAID parity drive.

RAID 10: Double your current storage space to determine the total amount of storage required.

Quiz #3Question 1:

True or False: Always use drives with the highest platter rotational speed available in your SAN system.

) True

B) False

Question 2:




Which of the following RAID levels uses a single dedicated drive for parity data?

) RAID 0

B) RAID 10

C) RAID 3

D) RAID 5

Question 3:

Using RAID 1 (mirroring) eliminates the overhead of parity calculations but has which of the following

isadvantages?

A) Data is at risk of a secondary failure during rebuilding.

B) The RAID system's overall read performance is reduced.

C) Costs increase because twice as much storage is needed.

D) Application performance is affected.

Question 4:

True or False: The backup window is the time that elapses from one backup operation to the next.

) True

B) False

Question 5:f the SAN volume using RAID has a lot of activity, and application performance slows, which of the following

RAID levels should you consider using?

) RAID 1

B) RAID 3

C) RAID 5

D) RAID 10

Question 6:

Which of the following backup types is the best compromise between backup window and number of data sets

o restore if recovery is needed?

A) Full backup

B) Differential backup

C) Incremental backup

D) Partial backup

Discovering SAN controllers, cables and connectorsSANs are made up of two main components: storage devices, in the form of disk and tape drives, and

etworking components, which include adapters, cables and switches. In this lesson, you learn about the

etworking components of a SAN.

Examining networking components of a SAN

n the past few lessons, you've covered the basics of the SAN infrastructure. In Lesson 3, you examined

rives—a SAN's data storage component—and options for using RAID to protect your data. In this lesson,

ou delve into the networking component of a SAN.

The term "network" can have different meanings, based on your background. For some, it means routers

nd a LAN connecting workstations and servers. However, in a SAN, it's a hidden network that users don't

onnect to directly. It's composed of the following:

ServersHost bus adapters

Cabling

Switches

Storage devices (disk arrays and tape drives)

You might be thinking that these components seem like the infrastructure that makes up a LAN. The

omponents do have similar names, and the connectivity between them might be similar. However, in a



SAN, the network is a high-speed channel designed to move data between storage devices to servers and

etween tape systems and storage devices. Figure 4-1 shows how these components are connected.

Figure 4-1: Networking components of a SAN.

Enlarge image

Host bus adapters

A host bus adapter (HBA) is a card or device added to a server to manage the transfer of information and

nable the server to communicate in a certain way. You're probably familiar with network interface cards

hat are used with desktops to communicate with a LAN via Ethernet. Similarly, wireless network interfaceards are used to connect laptops via Wi-Fi to a LAN. These HBAs provide a communication channel over

which data flows between a host and network devices.

SAN HBAs serve the same purpose: connecting servers to storage over a dedicated high-speed network

hat's separate from the LAN. However, HBAs are not simply network cards for your SAN. These cards

ffer high-speed processors that remove a large burden from the host's operating system and main CPU.

Creating a "virtual drive" for your server's operating system, the HBA and its driver software mask the

omplex communications that goes on behind the scenes between the HBA and the rest of the SAN.

Additionally, HBAs offer the ability to manage communications to the SAN in a way that increases the

verall throughput of your server's applications. The HBA creates multiple communications links to thetorage devices on the SAN and manages them separately. For example, if one application on your server

s transferring a large bulk of data to a SAN storage device that's under a heavy load, the HBA may have

o wait to send data to that storage device. However, another application on the server may be accessing

database that's not experiencing heavy loads, therefore the HBA can continue streaming the data

etween the server and the database without being affected by the other communications that are waiting.

Cabling

Data flows from a server's HBA over some type of cabling. This cabling can be copper, but often fiber-optic

abling is used for connectivity over longer distances and resistance to outside electromagnetic

nterference (EMI ). Copper cabling usually involves lower costs, but the main goal of a SAN is less aboutost and more about protecting data integrity. However, as you'll see shortly, the types of cabling used in

SANs can vary, depending on the underlying network infrastructure. For example, Fibre Channel

onnectivity uses fiber-optic cabling, and iSCSI might use copper cabling through existing switches.

Switches

Switches, the backbone of a SAN network, provide connectivity between servers and storage devices.

These devices are available in different networking technologies, and your decision on which one to use is

sually based on your current infrastructure and your selection of other SAN components. Next up, you

earn how to evaluate SAN networking technologies, considering factors such as available support, costs

nd flexibility.

Evaluating SAN networking technologies

Some LANs use networking technologies such as token ring, Attached Resource Computer network




ARCnet) and Fiber Distributed Data Interface (FDDI), but Ethernet is the technology of choice for most

rganizations. It offers interoperability and many vendors to select from.

For SAN networking, you can select from the following technologies:

Fibre Channel

iSCSI

InfiniBand

Each technology has benefits you should consider. Use the following factors as guidelines when you're

valuating SAN networking technologies:

Performance requirements: Is the connectivity speed of hosts an important factor? Can the SAN

infrastructure manage the throughput of all the hosts' needs?

Long-term strategy for applications: If the SAN is used for storing critical data, can you scale that

storage easily?

Availability or resiliency needs: Does the SAN require 24x7 support, or can you allow downtime for

maintenance? Does data need to be replicated to a remote location?

Support for server platforms: Does the SAN networking technology you've chosen support your

network's hosts?

Equipment cost: Although initial costs for equipment shouldn't be a high priority, given the SAN's

advantages in protecting data integrity, management might ask hard questions if costs are too high.

Management cost: Management time and personnel can be hidden costs. Does your staff need to be

retrained on the new technology? Make sure you allocate a budget for these costs.

Next, take a look at the major SAN networking technologies you can use, keeping these factors in mind as

ou evaluate them.

Fibre Channel

Fibre Channel can be considered the Ethernet of SANs and is the standard that all major vendors support.

t has been around for more than 10 years and is used in major corporations worldwide. If you want a

mature technology with wide support, Fibre Channel is an excellent option.

IT professionals everywhere are familiar with Fibre Channel, so it's a good option if you want a

standard SAN implementation with easy maintenance.

Fibre Channel does require an investment in switches and HBAs as well as fiber-optic cabling to connect

evices. However, this investment enables your organization to get full use of a SAN system that's built for

he future.

Some main benefits of Fibre Channel include the following:

Time-tested reliabilityBroad-based industry standard

Large install base

Standard for SAN systems

SCSI

A new contender in the SAN arena is Internet small computer system interface (iSCSI), an IP-based

tandard for linking storage devices over a network. The iSCSI protocol runs on top of a high-speed LAN

nfrastructure as another Transmission Control Protocol/Internet Protocol (TCP/IP) application, so you can

se your existing network for a SAN without having to build a new infrastructure.

iSCSI helps reduce SAN implementation costs and startup time by leveraging existing infrastructure

and familiar LAN cabling.

However, some potential challenges of using iSCSI include the following:



Competing with LAN traffic for available bandwidth

Requiring extra steps for installation

Redesigning your existing LAN to accommodate SAN components

When you use your current LAN infrastructure for a SAN's high-use traffic, competition for bandwidth could

e a problem. Printers, workstations and other servers might be affected by traffic bottlenecks if the

etwork isn't designed to handle the additional SAN traffic. When installing iSCSI, therefore, you might

eed to segment your network or add new switch ports to manage the SAN's extra storage devices. These

hanges could involve some network redesign, which may increase your time and effort. However, if your

etwork is already built for high-use traffic and is designed to handle new applications, such as a SAN,

SCSI can be an easy way to deploy a SAN with your current hardware and cabling.

nfiniBand

One of the newest SAN networking technologies is InfiniBand, which offers support from major

manufacturers but is still fairly new. Unlike the Peripheral Component Interconnect (PCI) bus used with

ther networking technologies, InfiniBand can carry multiple channels of data at the same time to improve

hroughput. With a low-overhead protocol and high-speed throughput, InfiniBand could overtake Fibre

Channel in the future.

The Infiniband specification provides for both copper and fiber optic cabling standards. With copper

abling, you have a limited distance of about 45 feet (or 15 meters) while fiber optic cabling provides for onnectivity up to 900 feet (or 300 meters). An organization investing in Infiniband technology for a SAN

would want to invest in the fiber optics to ensure that there are not expansion limitations once you've

mplemented your SAN.

Even with these benefits, you need to consider a few drawbacks. Because InfiniBand is still fairly new, its

upport isn't as broad as Fibre Channel support. Also, as with any emerging technology, some early-

dopter issues need to be worked out before InfiniBand can be considered ready for widespread use.

Currently, even with large names backing the technology, there are few second-tier providers that are

ffering products based on Infiniband. This may limit your options when your organization purchases

quipment to build out your SAN. InfiniBand could still be an excellent selection for your organization,

owever. Major companies, such as IBM, Microsoft, Dell, HP, Intel and Sun Microsystems use it, and it

as been used in super-computing applications around the world. However, compared to the FibreChannel support base, InfiniBand still can't be considered the standard SAN implementation.

After deciding which networking technology you want to use for a SAN, you need to select an HBA. Next

p, you learn some factors to consider when picking one.

Selecting an HBA

After selecting a SAN networking technology, the HBAs you decide to use have an effect on throughput

performance), reliability and scalability. In this section, you review some key decisions to make whenou're evaluating HBAs to use in your SAN.

Vendor recommendations

When you're building a SAN, consider HBA recommendations from the vendor of your SAN switching

ardware and storage devices. Vendors typically recommend their own HBAs for use in a SAN, but try to

et unbiased opinions from them, if possible. If not, most vendors have a list of supported HBAs on which

hey've tested their equipment, which you can find on their websites or in their support documentation.

Port speeds

While port speeds are a factor of both the HBA and the switch, you'll need to determine what speed you'll

e implementing. Often, this is a factor of pricing for the HBA. Faster cards are more expensive, and your

udget for these HBA cards could quickly be exhausted by purchasing the fastest cards your switch can

upport.



As a general rule, increase the budget for connectivity to storage devices where many servers will be

onnected while maintaining the more affordable connectivity for typical servers within a server farm.

Cabling type

As mentioned, you want to select an HBA that supports the cabling and other infrastructure components

ou're using. Most vendors offer the type of card you need for your platform. If you're using more

dvanced topologies, such as server blades, or a less common server platform, however, you might need

o use HBAs from different vendors to fit your network's needs.

HBA management tools

Most HBAs include configuration and management software. If you plan to use a single vendor for all SAN

omponents, managing HBAs over the SAN with the vendor's software is usually adequate. However, if

ou're using an enhanced management tool, make sure it supports the HBAs you've decided to use in

our environment. The HBAs you select may offer diagnostic options that will help keep your servers

eliably connected to the SAN. These HBAs can contact the management tools to offer a warning in case

he HBA is experiencing high error rates or memory issues.

Enhanced features

Some HBAs have enhanced features that offload tasks the main CPU might have to perform to

ommunicate on the SAN as described earlier in this lesson. These offload features, such as drive

irtualization and data transmission optimizations using a high-speed CPU on the HBA can dramatically

educe the load on a server's processors and improve its overall performance on the SAN.

Moving on

n this lesson, you learned about the major networking components of a SAN: HBAs, cabling and switches.

You also learned different options for SAN networking technology and factors to consider when selecting

n HBA. No matter what your choice for these components, make sure you consider factors such as

erformance, reliability and scalability so that your SAN can serve your organization's needs in the future.

Before you move on, do the assignment and take the quiz for this lesson.

Assignment #4

Review Lesson 4's list of factors to consider when selecting a networking technology for your

SAN, and then do the following:

Review Lesson 1's inventory to make sure you understand your network's needs.1.

Research the main networking technologies discussed in this lesson: Fibre Channel,2.iSCSI and InfiniBand. As you're researching, keep in mind the important factors to

consider and your current network infrastructure and requirements.

Select a SAN networking technology that best fits your organization's needs, and then3.

write a memo to management explaining your selection.

Quiz #4Question 1:

Which of the following is a SAN networking component? (Check all that apply.)

A) SwitchesB) Host bus adapters

C) Workstations

D) Cabling

Question 2:

True or False: Fiber-optic cabling should always be used in a SAN for protection against EMI.



) True

B) False

Question 3:

n what way does InfiniBand differ from other SAN networking technologies?

A) It can carry multiple channels of data simultaneously.

B) It uses your network's existing infrastructure.

C) It's considered the Ethernet of SANs.

D) It's been available longer than the other networking technologies.

Question 4:

Which of the following is a benefit of iSCSI networking technology? (Check all that apply.)

A) Wide vendor support

B) Reduced SAN implementation costs

C) Easy installation

D) Makes use of your existing LAN infrastructure

Question 5:

Which of the following factors should you consider when evaluating networking technologies for your SAN?

Check all that apply.)

A) Equipment cost

B) Management cost

C) Installation time

D) Performance requirements

Question 6:

Which of the following might require using an HBA from a different vendor to find one that fits your network's

eeds? (Check all that apply.)

A) Blade servers

B) Advanced management softwareC) Enhanced HBA features

D) Less common server platform

Exploring topologies and switchesThis lesson focuses on ways to interconnect storage network components. You'll learn about topologies and the

ole of switches and the services they provide. You'll also delve into more detail on the switches that tie a SAN

ogether.

Understanding basic topologiesn Lesson 4, you learned about the networking components of a SAN, such as host bus adapters, cabling

nd switches and the options you have for networking technologies. In this lesson, you explore some

ptions you have for designing your SAN.

A topology is a physical layout diagram showing how network devices are connected with each other.

Figure 5-1, for example, shows how servers and storage are connected.



asier. As you can see in Figure 5-3, however, if switch A fails, the devices behind it (labeled B and C) are

solated from the rest of the network and lose connectivity. Therefore, this topology doesn't work well for

onnecting storage devices.

Figure 5-3: A cascade topology might isolate devices behind a failed switch.

Mesh topology

The mesh topology, shown in Figure 5-4, is an excellent design for small SANs. By connecting each device

o all other devices, device or link failures don't isolate any device. However, as a network grows, this

opology can be expensive to expand and could become unwieldy to manage.

Figure 5-4: A mesh topology works well for a small SAN.

Core/edge topology

The core/edge topology is the most flexible and cost-effective option for building a SAN system. As Figure

-5 shows, it consists of a partial mesh between devices on the SAN; it's not a full mesh because not all

evices are connected to each other. Devices at the edge of the SAN are connected to edge switches,

which are connected to core switches. Because each edge switch is connected to at least two core

witches, a link or core switch can fail without isolating devices on the network. When you need more

onnectivity between devices, this design can be expanded easily by adding edge switches to core

witches.



Figure 5-5: A core/edge topology.

n addition to selecting a physical layout for connecting SAN device, you need to consider other factors in

our design. As you learn in the next section, one important consideration is incorporating redundancy into

our SAN to make sure you don't lose critical data after a network failure.

Continuity management options

Organizations sometimes overlook the need to consider operational continuity, which is the capability to

esume operations after a disaster. One way to ensure operational continuity is to build redundancy (alsoalled resiliency) into your SAN. Although adding redundancy increases costs, being able to maintain your

rganization's operations after a network failure is essential. To help you determine how much redundancy

ou need, ask management the following questions:

What's the organization's cost per hour during normal operations?

How does storage downtime affect the organization's operations?

How long can the organization tolerate unplanned downtime?

How much is the organization willing to spend to avoid unplanned downtime?

With this information, you can better estimate the financial impact of unplanned downtime and budget for a

edundancy solution. The following table compares costs and redundancy features of the major topologies

o help you make a decision.

Factor Ring topology Cascade topology Mesh topology Core/edge topology

Tolerance to failures Poor Poor Good Good

Performance Good Good Better Best

Scalability Some Some Poor Good

Cost Low Low High Medium

Table 5-1: Comparing topologies.

Redundancy within a topology permits individual failures to reduce the likelihood that connectivity to one or

more components are lost. If your organization has a low-tolerance for unplanned downtime due to its

xpense or criticality, spending more on a topology that offers good redundancy would offer a way to

educe the amount of unplanned outages. Obviously, the more redundant the connectivity is, the more

omponents that need to be purchased, installed and maintained over time.

After selecting a topology, you have other options for adding disaster recovery features. For example, if

ou use a core/ed e to olo , ou could desi n a multi-buildin SAN that can isolate switch failures to a



pecific building or floor, as shown in Figure 5-6. Being able to isolate switch failures improves

erformance and redundancy because a single failure doesn't affect the entire network. Also, if you plan

horoughly, you could expand your SAN to favor local hosts based on their proximity. By adding storage

evices that are connected to local edge switches rather than connected to a switch on the other side of a

ore switch, you could reduce the amount of traffic flowing over the core switches, which allow more

hroughput for connections that have to traverse the core switches.

Figure 5-6: A multi-building SAN that incorporates core and edge switches.

Networking technologies haven't been mentioned because they usually have no effect on the SAN

topology you select. If you're creating an iSCSI SAN on top of your existing LAN, however, you might

need to consider whether your current LAN topology is capable of handling the extra SAN traffic.

Now that you understand how to select a topology, keep reading to learn what features to look for in SAN

witches to create your network topology.

Exploring switchesBecause SANs in a core/edge topology with Fibre Channel networking technology are the most common,

his section uses this setup to explain switch features you should consider for your SAN. SANs that are

uilt on a LAN using iSCSI would have similar topology considerations. In addition to the SAN traffic, the

AN switch design would also need to incorporate heavy usage internet and intranet traffic as well as

rinters and workstations. The same core/edge switch design would apply to an iSCSI SAN.

Basic switch features

SAN switches have several basic features that provide connectivity for edge devices, such as servers and

torage, as well as core switches. Each connection, or link, to a switch is made over a copper or fiber-opticable. One end connects to the network device, and the other connects to the switch port. You can set the

onnectivity speed on a switch port manually or configure it to negotiate the highest possible speed

utomatically.

n addition, other integrated components are used to report the status of a port and manage ports remotely

y using desktop or web-based management software. Typically, high-end switches have more

management and reporting features, but many entry-level switches incorporate these helpful features, too.

Web-based management software is a convenient alternative to desktop software but might not offer

as many features such as auto-discovery or real-time statistics.

Environmental factors have become a concern lately, so reducing power consumption and cooling

equirements is an important consideration. Most vendors now offer energy-efficient switches with reduced

ower consumption and cooling. In addition, look for power supply redundancy options to increase your

etwork's capability to withstand electrical fluctuations or outages. Even entry-level switches now offer

edundant power supplies that can be plugged into two different circuits in the data center.



Zoning

You can set up zones for switches that enable you to segment traffic for improving security and conserving

andwidth. If you create a zone for financial data, for example, only servers added to the financial zone

ave access to storage in that zone. With this setup, you can help prevent unauthorized access to financial

ata, which improves security.

n addition to creating zones to secure data, adding zones can reduce the likelihood that any one storage

evice gets overloaded. By creating multiple zones and assigning devices and servers to each zone, youan break up the traffic going to each of the devices so that requests are services more quickly and the

raffic within that zone is managed. If your organization created only one zone for all devices, it may be

ossible that the servers within the SAN could saturate the bandwidth to the storage devices.

Devices can be a part of more than one zone, too. For example, if you want all devices in your SAN to

hare the backup system, you could configure all devices to be part of the backup zone to give them

ccess to the tape backup unit. Zoning is a powerful tool for managing servers and data and is discussed

n more detail in Lesson 6.

SL trunking

nterswitch links (ISLs) are another option for connecting SAN switches. Switch links are combined to

reate a "trunk" or bundle of links that act as a single connection. This option increases bandwidth, so it

an handle more traffic. Also, it improves redundancy because if one link fails, other links in the trunk can

ontinue transmitting data. Figure 5-7 shows an ISL trunk in a topology diagram.

Figure 5-7: ISL trunking combines several switch links.

Enlarge image

f you're building a SAN that uses a different technology (such as 10 Gigabit Ethernet with iSCSI), make

ure you look for the same types of features discussed in this section. Many major vendors support these

eatures in iSCSI products to give you the same flexibility and capability of Fibre Channel SANs. Your

urrent LAN switches may already be capable of some of the features listed in this section which would

llow your organization to more easily implement an iSCSI solution.

Moving on

n this lesson, you learned some topology options for connecting SAN components. In addition, you

earned the importance of incorporating redundancy into your SAN topology and reviewed some features to

onsider when purchasing a switch. Lesson 6 puts together what you've learned in previous lessons and

eviews management options for your SAN. Before you move on, do the assignment, take the quiz for this

esson.

Assignment #5

For this assignment, do the following:

Review your organization's needs by looking over your assignments for previous1.




lessons—selecting a RAID level, networking technology and so on.

Using paper and pencil or a drawing program, design a SAN topology that satisfies your 2.

organization's needs for cost, scalability, performance and redundancy (capability to

tolerate failures).

Write a memo to management explaining your selection of a SAN topology.3.

Quiz #5Question 1:

Which topology can be unwieldy to manage when the network expands?

) Mesh

B) Cascade

C) Core/edge

D) Ring

Question 2:

True or False: Devices can be part of only one zone in a SAN.

) True

B) False

Question 3:

To plan for incorporating redundancy into your SAN design, what information should you get from

management? (Check all that apply.)

A) How long unplanned downtime can be tolerated

B) Effect of downtime on the organization's operations

C) Cost per hour of normal operations

D) Budget for preventing downtime

Question 4:

How can you expand a core/edge topology easily?

A) Add edge switches to core switches.

B) Add more ISL connections.

C) Add core switches to edge switches.

D) Set up more zones.

Question 5:

SL trunking offers which of the following advantages? (Check all that apply.)

A) Increased bandwidth between switches

B) Shorter distances between switches and end devices

C) Improved redundancy

D) All of the above

Question 6:

Which of the following is a disadvantage of web-based management software for switches?

A) Difficult to learn

B) Inconvenient to use

C) Usually offers fewer features

D) Available only for high-end switches

Managing and administering SAN softwareSAN systems require management to keep them running smoothly. This lesson covers using management

oftware, zones, policy-based tools and LUN masking to ensure your SAN is secure and functioning efficiently.

Exploring SAN management software



n Lesson 5, you explored SAN topologies and learned more about switches, which provide connectivity

or your SAN. To take advantage of all the power a SAN offers, in this lesson you learn how to select the

est management software for your solution and explore other options for managing your SAN.

Most SAN vendors have different packages of management software with features for administering and

eporting on SAN resources. These packages can be divided into three major categories:

Web-based software

Low-functionality workstation software

Premium-functionality workstation software

The following sections explore features of each category.

Web-based software

Web-based software usually has fewer features than workstation-based software. It can perform simple

asks and basic reporting but typically isn't used for an enterprise-level SAN system. Web-based software

oes offer the following benefits, however:

No software to install

Can be used from any workstation or even a remote location

Performs simple tasks easilyTypically free or included with equipment purchase

For a small or highly mobile organization, web-based software can be the perfect management solution.

Low-functionality workstation software

ow-functionality workstation software generally offers more resource-allocation functions than web-based

oftware. In addition, some low-functionality software can generate a topology map of your SAN and

eports for every device. The software must be installed from a CD/DVD and is usually run from an

dministrative workstation. Some vendors will include this type of software for a modest fee. Other

endors may even freely distribute a limited version of their premium-functionality software. Even if there is cost to this software, the added benefits are often worth the small cost. Most low-functionality software

lso includes the following features:

Produces a complete picture of your SAN resources for better visualization

Manages multiple switches

Automates tasks for efficient use of staff time

Uses industry-standard interfaces to manage multi-vendor platforms

Premium-functionality workstation software

Premium-functionality workstation software adds more enterprise-level features for capacity, performance

nd reporting. This software is typically more expensive than the low-functionality software discussedreviously. But the added costs for the premium-functionality can often provide a great deal of added

enefit in terms of efficiency. Software in this category enables you to do the following:

Plan for allocating storage capacity

Support storage infrastructure lifecycle management

Monitor performance of your SAN components

Get notifications for events such as low disk space or high resource use

Keep in mind that vendors release updated software versions constantly to stay competitive, so you might

e able to find some high-end features in a less expensive low-functionality package. Make sure you do

our homework on which features are important to your organization when evaluating management

oftware for your SAN. If you decide to purchase a premium-functionality package, make sure your

rganization really needs the features that it's paying for.

Now that you know what to look for in management software, keep reading to find out other management

ptions you have for your SAN.



Managing resource access

Managing resource accessibility is critical to maintaining SAN security. You can manage resource access

y designating device zones and LUN masking.

Designating device zones

As you learned in Lesson 5, you can divide your SAN devices into zones to make sure data is accessible

nly to resources allocated to a zone. A small SAN might have only one zone, but larger SANs could have

many zones. Zones are useful for simplifying management and increasing security.

You can compare using SAN zones to setting up groups to manage user rights. When you're assigning

ermissions to users for network resources, often you set up user groups to make this task easier. That

way, you don't have to assign permissions separately to each user. You assign permissions to a group

ou create, and then add users to the group as members.

The same is true of SAN zones. You can assign devices to zones as an easier method of managing rights

o storage resources. As with users who can be members of more than one group, devices can be placed

n more than one zone so that they can access several different storage resources. Tape backup systems,

or example, are typically given rights to all, or many, zones to make the backup process more efficient.

Figure 6-1 shows a switch assigned to both Zones A and B.

Figure 6-1: A device can be assigned to more than one zone.

You can create the following types of zones, explained in more detail in the following sections:

Hard zoning

Soft zoning

World Wide Name zoning

Hard zoning

Hard zoning, the strictest type of zoning, is configured in the device hardware and actually preventsevices from communicating and accessing resources outside their zones. Because it's implemented in

ardware, it's fast and secure. Consider hard zoning for highly confidential information, such as financial

ata or personnel records. one drawback of hard zoning is its lack of flexibility. After you've configured

oning for device hardware, changing zones can be more time consuming than with other zoning types.

Soft zoning

Soft zoning, as the name implies, is configured in device software as a filter for accessing resources. With

his type of zoning, when a device "sees" the SAN, it can see only the resources it has allowed to access

n its zone. Therefore, modifying your setup to add or overlap zones is easier than with hard zoning. Soft

oning is less secure because servers or devices in other zones might be able to guess device addressesdiscussed in the next section) and access resources outside their zones. However, most SANs aren't

pen to network devices outside the SAN, so this disadvantage isn't major for most organizations.

Worldwide naming zoning



An even more flexible zoning type is World Wide Name (WWN) zoning. A WWN is a unique identifier

ssigned to the HBAs of SAN devices, and resource access is then filtered based on WWN. With this

oning, you can recable a SAN if needed without re-assigning ports and devices to the correct zone.

Management is easy with this zoning type, but a rogue HBA could be added to the SAN and use a valid

evice's WWN to access sensitive information.

Next up, you learn about another option for streamlining management: LUN masking.

LUN masking

Another useful option for easing SAN management is logical unit number (LUN) masking. You give each

evice in a SAN a unique LUN identifier for addressing and allocation purposes.

So why would you need to hide, or mask, a LUN address? Contrary to what its name implies, LUN

masking isn't done for security reasons. Mainly, it's used to prevent Windows servers from trying to write

heir own volume labels on non-Windows devices, such as Linux or UNIX. This attempt to write over LUNs

n other devices can cause corruption of data stored on them. In addition, if a LUN is written over with a

Windows volume label, you might not be able to use that device on another platform besides Windows.

f you mask a device's LUN address, Windows servers don't recognize the device as non-Windows and

on't attempt to overwrite the address. You can then unmask the LUN as needed for other non-Windows

ystems using that LUN. Premium-functionality management software and some low-functionality versions

an handle LUN masking automatically for you.

mplementing policy management

As you've learned throughout this class, you have several SAN components to manage, both physical and

irtual: zones, addresses, ports, links, switch connectivity, bandwidth, storage allocation and more. All

hese management tasks can be overwhelming for SAN administrators.

Using aliases

To simplify these management tasks, you can use policy-based management tools to handle many

unctions automatically. For example, instead of allocating storage or zones only by using WWNs or LUNs,

which are usually strings of letters and numbers, you can create an alias, such as Sales Server, that's

asier to remember. In other words, your management software keeps track of WWN or LUN addresses

o that you don't have to.

Giving devices easy-to-remember aliases makes SAN management easier.

Using policies

You can also set up policies, or rules, that automate which resources are assigned to certain zones or

erform routine configuration checks to make sure resources are allocated correctly.

Additionally, policies can help manage alerts to conditions that may affect the servers or the storage on the

SAN. For example, you could set a policy that sends alerts based on when a volume approaches some

apacity threshold. Typically policies can be set on the following general types of conditions:

Availability: Setting the number of redundant paths to data within the SAN

Backup: Specifying how often to back up certain volumesCapacity: Alerting when a volume becomes too full

Interoperability: Alerting when devices may not work with other devices on the SAN

Performance: Monitoring application-level response times to ensure service-level agreements

Security: Setting the permissions on which servers have access to particular storage resources using

zones and LUN masking

Because SAN management software enables you to abstract and consolidate resources, you can manage



more resources with fewer people. The reporting features in this software are also useful for auditing your

SAN to ensure consistency and monitoring performance.

Now that you understand the options for managing a SAN, you're ready to build a SAN for your

rganization's storage. The next section reviews what you need to know to be successful.

Starting smart with your SAN

This section wraps up the class by reviewing guidelines for setting up and using a SAN solution. Withhese guidelines, you can start smart and create a SAN that serves your organization for years to come:

Assess your overall storage needs for the organization, not just by department.

Plan for storage growth to make sure you're purchasing cost-effective storage devices.

Review your options for networking technologies, and then pick one that provides the performance and

support you need.

Determine how you're going to migrate data to your new SAN, and then plan for how your server

resources will be affected during the transition.

Select a SAN solution that's the right size for your organization but is capable of growing to meet your

storage expansion needs.

If your organization doesn't need a high-end solution, remember that an all-in-one solution might be a

good fit.

Select a RAID level that protects your data yet offers the performance your applications need.

Use a backup solution that can read data directly from the SAN.

Select a SAN topology that offers the growth, performance and redundancy options your organization

needs.

Use SAN management software to streamline access to common functions and make configuring

security and storage capacity easier.

Document your network by using the management tools you've selected.

Review your growth and capacity planning objectives often to make sure you have storage ready when

your organization needs it.

Moving on

n this lesson, you've learned how SAN management software can ease the administrative burdens

ssociated with a SAN and reduce the personnel needed to manage your storage infrastructure. As

lways, take the quiz and do the assignment before moving on.

Assignment #6

Now it's time to put together everything you've learned in this class. Review the guidelines at the end of

esson 6 to help you determine the best SAN solution for your organization. Then starting with the

opology diagram you've created for Lesson 5's assignment, expand this diagram to illustrate your entire

SAN system. Label all hardware components, such as cabling, switches, backup devices, HBAs and

torage units, and then include the model and make for each device. Finally, put together a proposal for

management that specifies the networking technology, redundancy features and SAN management

ptions you're using and then include a cost estimate for your overall SAN solution.

Quiz #6Question 1:

Reconfiguring zones is easy with which type of zoning? (Check all that apply.)

A) Hard zoning

B) WWN zoning

C) LUN zoning

D) Soft zoning

Question 2:

True or False: Low-functionality workstation software is the best solution for a small or highly mobile

rganization.

) True



B) False

Question 3:

Why should you use LUN masking?

A) To improve security

B) To create an easy-to-remember identifier for devices

C) To prevent Windows servers from overwriting LUN addresses with their own volume labels

D) To allow Macintosh and UNIX devices to work together

Question 4:Which of the following is the most restrictive type of zoning?

A) WWN zoning

B) Soft zoning

C) Strict zoning

D) Hard zoning

Question 5:

True or False: Policy-based management tools handle certain tasks automatically, so you can manage more

esources with fewer people.

) TrueB) False

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