all about sans

Comparing SAN protocols

SANshopping list

SANsand virtual environments

Data Storage InsightsData storage strategies and insights for growing businesses

All About SANs

Issue 3, 2011

In this issue:

2 All About SANs

3 Comparing the Most Popular SAN Protocols

6 The IT Administrator’s SAN Shopping List

9 Why SANs Make Sense for Virtual Environments

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9

2

6

Contents…

Contributors: Drew Robb and Paul Rubens.

Data Storage Insights

2 Data Storage Insights: All About SANs © 2011, Internet.com, a division of QuinStreet, Inc.Back to Contents


torage area networks (SANs) are one of the options that growing businesses can turn to when it’s time to upgrade their storage infrastructure. As with any major technology

purchase, it’s important to do your homework when shopping for a SAN.

In this issue of Data Storage Insights we’re going to review the most important aspects of a SAN to help IT managers make an informed purchase. We start with a comparison of the two most popular SAN protocols — Fibre Channel and Internet SCSI (iSCSI) and the case for using either protocol in your business.

We’re also going to review a checklist of the things that IT administrators need to know when shopping for a SAN, including a review of disk arrays, management software, host bus adapters, storage switches and more.

Finally, we’re going to look at networked storage for your virtual environment and why a SAN is the smart choice to make. Many growing businesses are beginning to explore server virtualization if they aren’t already using it in their data centers. How they will store data in this virtual environment is a question that needs to be answered early in the process.

After exploring the ins and outs of storage area networks with this issue of Data Storage Insights, you’ll be in a better position to make an informed buying decision.

All About SANs

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ost storage area networks (SANs) are deployed using one of two protocols: Fibre Channel (FC) or Internet SCSI (iSCSI).

“iSCSI and FC are both block transfer protocols that transmit the SCSI command set across a network to create a storage area network,” said Howard Marks, Founder and Chief Scientist at DeepStorage.net.

But which is a better fit for your business’s data storage needs? Like most questions of this nature, the answer depends on a large number of factors.

The Case for iSCSI

iSCSI uses standard Ethernet and Internet Protocol (IP) to transport the SCSI commands. As such, one of the big advantages of iSCSI is that it leverages the same network knowledge that organizations already have in house. In other words, for organizations that don’t have FC know-how within the enterprise, the deployment of an iSCSI SAN will be a whole lot easier as existing personnel should be able to install and manage it without having to learn new skills.

“If you’re not already using FC I can see very few environments where I would advise building a new FC infrastructure,” said Marks. “By using iSCSI, you can save money and avoid having to send some of your administrators off for Fibre Channel training.”

Fibre Channel, on the other hand, is a network architecture used only for SAN transport. Companies deploying it have to employ SAN administrators as the technology is very different from traditional networking.

“Most network guys find FC arcane at best,” said Marks.

“It requires additional knowledge and training.”

Hiring staff with sufficient FC SAN savvy, therefore, is a factor that has to be considered for those looking to deploy a SAN. And those personnel probably won’t come cheap. But that isn’t the only added expense that goes along with FC. Marks characterizes Fibre Channel gear as being significantly more expensive than its Ethernet equivalent. It requires its own switches, Host Bus Adapters (HBAs) and disk arrays that can be a daunting investment for those establishing their first SAN. That’s a big reason why many SMBs gravitate to iSCSI as their first foray into advanced storage networking.

The Case for Fibre Channel

But it isn’t an open and shut proposition. The big reason why an FC SAN is necessary in some shops boils down to performance.

Comparing the Most Popular SAN ProtocolsBy Drew Robb

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“Fibre Channel can deliver lower latency and therefore better performance for the most demanding applications,” said Marks.

That’s why boutique financial businesses and other IT-centric firms often bypass iSCSI and implement an FC SAN. While the initial cost may be higher, they gain in the long run due to improved transaction times. The price tag for the SAN is dwarfed by the revenues that can potentially be lost due to slow transaction times.

In addition, server and storage OEMs are doing a better job of packaging their hardware to make it more affordable. Mergers within the industry have resulted in a steady fall in the price of introductory FC SAN hardware, making it a more attractive option, particularly for those with higher performance requirements.

Blurring the Lines

While those are the traditional arguments concerning iSCSI versus FC, the lines are blurring as technology advances. On the iSCSI side, the latest bump in Ethernet speed goes a long way to resolving its performance shortfall. Instead of the usual 1 Gb speeds, a newer standard known as 10 Gb Ethernet (10GbE) provides a major hike in throughput. That has caused some to wonder if Fibre Channel really has a future.

But 10 GbE gear also comes at a premium, though prices are gradually falling. Further, firms deploying this new iSCSI platform may find that their existing infrastructure just isn’t up to the task.

“iSCSI over 10 Gb Ethernet provides more performance than a two-socket Intel Xeon server can use,” said Marks.

His suggestion is that FC is preferable for organizations with more than 200 servers, as a robust SAN means they can take advantage of the additional management tools available for FC while maintaining expected performance levels.

Tom Hammond-Doel, Vice Chairman of the Fibre Channel Industry Association (FCIA), points out another

plus for FC. Its large installed base gives it a unique position that distinguishes it from other storage transport technologies. This has led to a steady stream of FC features and enhancements that promise to give iSCSI a run for its money in the coming years. While most existing sites use 1, 2 or 4 Gb FC, newer gear featuring 8 Gb FC already dominates in terms of number of ports shipped, according to Dell’Oro Group numbers. And within a couple of years, 16 Gb FC and Fibre Channel over Ethernet (FCoE) ports will take the lead.

FCoE even threatens to eliminate the entire iSCSI versus FC argument as both protocols utilize an Ethernet network. The advantages of FCoE are less hardware, cabling, installation, management and lower cost by reason of converged storage and networking infrastructure.

“When you take switches, cabling and adapters into account, FCoE is 33 percent cheaper to deploy than traditional networks and holds the promise of 50 percent savings on power and cooling,” said Bob Laliberte, an analyst with Enterprise Strategy Group (ESG). “Long term predictions are that most connectivity options are focused on Ethernet-based transports.”

ESG placed adoption of this technology at only 9 percent of users at the end of 2010. That should rise to more than 25 percent by the end of near year. The reasons for the relatively slow ramp up include cost and technological maturity. The vendor world has been taking its time bringing FCoE products to market; and those implementing it face a significant amount of costly infrastructure change-out and upgrade. Yet the promise of FCoE is enticing: a single network that can run iSCSI on IP plus FCoE concurrently.

But not everyone is convinced that Ethernet will eventually gobble up all FC traffic. The FCIA is pushing along its roadmap for 16 Gb and 32 Gb Fibre Channel. The association is aiming for 32 Gb products to hit the market by around 2014. They will come with a host of new features including higher levels of management sophistication, storage virtualization and energy efficiency.



Summary

The question about whether to deploy iSCSI or FC used to be a simple matter. But innovation on both sides has clouded the issue. Those attempting to reach a decision are advised to find a vendor or partner that offers both technologies as they can help determine which protocol will provide the most value within a specific environment.

In some cases, it may turn out that the answer is a combined implementation of FC and iSCSI.

Stuart Miniman, a Principal Research Contributor for The Wikibon Project, even goes so far as to state that it is a false argument to pit iSCSI vs. FC (or FCoE).

“iSCSI is generally is small environments with a management team that handles the full spectrum of server/storage/network while FC deployments are typically much larger and are managed by a dedicated storage team,” said Miniman. “There are lots of customers that use both — FC for the bulk of storage and iSCSI for branch office, test/dev or other environments where it makes sense.”



“Disk arrays also support various availability features including different RAID levels, snapshots, replication and high availability such as dual controllers and failover capability,” said Greg Schulz, an analyst with Server and StorageIO Group.

Storage Switches

It is the storage switch that provides the secret sauce that creates the SAN “fabric.” These switches come with multiple ports of various kinds to connect all the cabling. These switches route data from the servers to the disk arrays.

Some SAN switches are dedicated to a particular protocol or interface such as SAS or Fibre Channel while others such as iSCSI or FCoE can use Ethernet or enhanced Ethernet based switches. Some SAN

switches support a mix of Fibre Channel and Ethernet for iSCSI (or NAS) as well as Fibre Channel over Ethernet (FCoE), which is gaining in popularity.

For those only using an iSCSI SAN, basic Ethernet switches may be enough. Some experts recommend dedicated switches for the iSCSI SAN rather than sharing them with the network. Others suggest server upgrades, though, that is not always necessary.

“For the majority of x86 servers, your existing 1Gbps Ethernet gear is fast enough to use for iSCSI, too,” said Howard Marks, Founder and Chief Scientist at DeepStorage.net.

The IT Administrator’s SAN Shopping ListBy Drew Robb

t’s time to invest in a storage area network (SAN) to increase your storage capacity and improve efficiency. It is vital, therefore, to understand what to look for in a SAN before

deciding where to invest storage resources. Here are some items to consider in the SAN shopping list.

Disk Arrays

Disk arrays form the backbone of any SAN. They host large quantities of data that can be accessed by any server in the company. As well as proprietary software, controllers and other gear, the disk array contains a large number of disks — either high capacity but slower SATA, speedier SAS (but with lower capacity) or Fibre Channel disks (FC) that offer the highest performance. Further, arrays are available that mix and match these kinds of disks into tiers of storage so that key applications are given priority on faster disk. There are even models on the market these days that include Solid State Drives (SSD) that operate at close-to-memory speeds.

Obviously there is a price premium for SSDs, as well as FC disk. It’s a case of buying what your applications need and what you can get away with based upon your budget. Some arrays, after all, come with million-dollar plus price tags. But that level of functionality is rarely needed at every business. Many disk arrays are attractively priced yet offer a decent amount of room for storage expansion. Features can vary greatly from one model to another.

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Host Bus Adapters

Host bus adapters (HBAs) are necessary to connect the SAN to the servers. Essentially, an HBA is a circuit board or adapter that provides input/output processing and physical connectivity between a server and the storage. HBAs typically install into a PCI, PCIx or PCIe server slot or via a mezzanine card in a blade server with various combinations of ports, protocol supports and other functionality for security or management. Some HBAs are for SAS, others for FC, iSCSI or on an increasing bases converged network adapters (CNA) that support a mix of FC, FCoE, iSCSI and NAS concurrently using a mix of copper and optical cabling.

Cabling

Optical transceivers as well as fiber optic, copper cabling or Ethernet cable is required to connect everything, of course. For more advanced environments, basic and complex cable management systems are available to supplement basic cable tagging approaches.

“Don’t skimp or try to save costs on your SAN by buying cheap cables, and take care with them including keeping connectors in good shape,” said Schulz. “One loose connection, piece of dust or debris can render your SAN in peril.”

Management Tools

Various SAN components come with their own management tools, some of which provide configuration, diagnostics, reporting security and provisioning for other components.

Expertise and Experience Level

But it isn’t just cables, tools and components. You have to know what you are doing. Those buying their first SAN are typically not going to be experts in the technology inside. Therefore, it is important to understand that some gear is meant for experts and others for beginners. Opt for the latter category.

“Many of the arrays and switches used in large enterprises are designed to allow highly skilled storage admins to tune them within an inch of their lives for particular applications,” said Marks. “If you’re not already a crackerjack disk jockey you’re better off with a system designed to be easy to use and self tuning.”

He adds that the technology for self-tuning has improved to the point that today’s disk arrays are better at tuning than 80 percent of the storage admins out there.

Capacity vs. Performance

It is also essential to balance the SAN’s capabilities to your needs. Benjamin Woo, an analyst at IDC, says that an oft-used metric in storage purchasing — cost per gigabyte of storage capacity, is sometimes a “poor metric.” He gives the example of System A having 20 TB and costing $60,000 whereas System B with 30 TB costs the same price. System B with a lower price per TB would win the bid. But what about its number of Input/Output operations per second (IOPS), throughput, reliability and scalability? Going back to the example, he said that System A actually included Solid State Disks (SSDs) and therefore has a much lower cost per IOP. Bottom line: performance has to be taken into account as well as capacity. Those with no high-performance requirement can afford to deal in cost per GB. Otherwise, application performance has to be factored in to the buying equation using metrics such as IOPS.

“Performance is great if you need it and can use it,” said Schulz. However if your applications cannot realize the full potential due to software, server or other bottlenecks, you will not realize the benefits from a fast SAN.”

More Buying Tips

Marks said that once you reach the point where you are spending $50,000 or more on a disk array, you should be aware that there may be wiggle within the pricing structure.

“There is a lot of negotiating room especially in the last



few weeks of the vendor’s quarter,” said Marks.

Another suggestion, he said, is to separate out the nice-to-haves from the vital by paying attention to implementation timelines.

“If you can’t get an approval from telecom for a WAN link for a year, don’t let the replication software drive the purchase,” said Marks. “You might never get it running.”

For those shopping for an FC SAN, though, pay close attention to the Hardware Compatibility List (HCL), which is typically issued by the disk array vendor. Any switches, HBAs and other gear have to be on the HCL. Therefore, it is usually best to begin with the array and work back from there in purchasing.

Otherwise, Marks adds some advice for those who already have a SAN and are considering upgrades.

“If you have an FC SAN, adding another array and staying with FC would be a smart idea,” said Marks.

Keep in mind, though, that fast SANs need fast servers, fast servers need fast storage, fast storage needs fast networks and any speed bump or road block results in lost opportunity on your SAN investment.



Why SANs Make Sense forVirtual Environments

By Paul Rubens

irtualization technology offers many important business benefits, including lower capital and facilities costs; greater flexibility; higher availability; efficient backup capabilities; and

effective disaster recovery. For these reasons the majority of large enterprises have begun to virtualize at least some of their IT infrastructure, and as the technology becomes more mature and affordable, it is becoming increasingly attractive to growing businesses as well.

That means that if you’re planning to upgrade you storage systems, it makes sense to future-proof your investment by ensuring that anything you purchase will be compatible with, and allow you to reap the full benefits of, virtualization.

To understand how the storage requirements of virtual server environments differ from those of traditional server environments, let’s take a closer look at a typical (non-virtualized) server setup. In small businesses servers simply make use of internal hard drives, and as storage requirements grow over time these are augmented by the addition of direct attached storage (DAS) devices. If storage requirements increase further the next step is commonly to upgrade to a shared storage system using network attached storage (NAS) or devices.

In a non-virtualized environment NAS solutions work well because end users typically access small files such as documents or spreadsheets from the NAS over the local

area network, and applications like corporate databases also access larger files from the NAS from time to time. A typical NAS setup is perfectly suited to this type of environment where individual machines make single reads or writes of data to and from the storage system on a regular basis, throughout the day.

But when you begin to introduce a virtualized server environment into your organization, demands on your storage systems can change dramatically. For smaller companies or those with a limited virtualized environment a typical NAS device can continue to provide a very effective and cost efficient storage solution, but as the business grows or in a larger virtualized environment a single physical host can be sending out tens or even hundreds of requests for data at any one time. What’s more, these requests will occur on a highly random, rather than regular, basis. If you’ve got a number of physical hosts, each

supporting half a dozen or more virtual machines, then this will place a heavy burden on your storage system. You run the risk that the NAS device will turn into a bottleneck and your local area network could struggle to cope with these bursts of storage traffic.

That means that if you want to upgrade your storage systems to a solution that will enable you to get the full benefits of virtualization as your company expands, a storage area network (SAN) may be a more suitable option. That’s because a SAN has its own dedicated

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high bandwidth network for moving data to and from the physical computers hosting virtual machines— often based on iSCSI in smaller SAN installations, and a SAN may also be better suited to coping with the levels of data requests that a busy virtual server setup will throw at it.

Specific Benefits of Shared Storage in a Virtual Environment

In virtualized server environments, virtual machines exist as data files that run on physical hosts, but which can actually be stored on a SAN or fast NAS. This opens up the possibility of using some sophisticated virtualization technology to bring you some valuable business benefits — if your storage system supports it. These include:

Instant Failover

Perhaps the most valuable benefit of employing a SAN (and, in some circumstances, NAS) in a virtualized environment is the ability to have highly available virtual machines that can continue to run without interruption, even if the physical host running the virtual machine fails unexpectedly. This technology is called vMotion in a VMware virtualization environment and Live Migration in a Microsoft Hyper-V environment. In the event of a server hardware failure the virtual machine file stored in your SAN or NAS can be redirected to run on alternative hardware automatically without the need for the virtual machine to be stopped.

Backup and Disaster Recovery

Another key benefit of using a SAN or NAS in a virtualized server environment is the ease with which virtual machines can be backed up or recovered in the event of a disaster. That’s because, as mentioned above, virtual machines exist as a single virtual machine file stored in the storage system. That means that individual virtual machines or your entire virtual machine fleet can be backed up simply by copying the appropriate virtual machine files across the SAN or NAS, without any impact on local area network traffic. These files can also be copied to tape and physically moved off site, or copied over a wide area network link to another SAN at a remote location

for business continuity and disaster recovery purposes. In the event of a disaster the virtual machine files can be run from new physical hosts at a secondary site or on machines rented from a business continuity service provider.

Application Awareness

Some SAN devices come with management software that enables application awareness in virtualized environments. This is a technology that allows the storage system to recognize data from particular applications, and to analyze the data’s usage patterns to optimize how and where that data is stored and backed up on SAS, SATA or SSD disks. This can provide significant storage cost savings by matching data to the most appropriate storage media, and can also improve performance for some data-intensive applications significantly.

SAN Software

For companies with limited experience with virtualized environments it makes sense to look for a SAN solution designed with virtualization in mind, and which comes with software that integrates with the major virtualization systems from VMware, Microsoft and Citrix. Doing so ensures that the SAN will fully support the virtualized server environment and make it easy to carry out functions such as uninterrupted failover, as well as data protection, point in time data snapshots and functions, and transparent data migration between different storage devices.

Scalability

Many companies that introduce server virtualization quickly discover that their storage capacity requirements grow very rapidly. There are a number of reasons for this, including a rapid expansion in virtualization once the technology and benefits become better understood, and the need to replace internal storage and DAS devices with shared storage. For this reason it’s important to choose a storage solution, whether SAN or NAS-based, that is easily scalable and which can be upgraded easily, preferably without requiring periods of downtime.



Summary

Growing businesses that aren’t yet taking advantage of virtualization can expect to be adopting virtualization in the near future. In order to be prepared and to protect their storage investment, these businesses should consider adopting a SAN to serve their virtual server environments.

SANs have an ability to provide disaster recovery, work around hardware failures and scale to meet the needs of growing businesses that make them a worthwhile investment for businesses that need to adopt a new storage infrastructure for their virtual environments.

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