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Chapter 2
Presented by:
Anupam Mittal
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Storage Systems Environment: Components of a Storage System Environment
Storage System Environment - 2
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Upon completion of this chapter, you will be able to:
List components of storage system environment◦ Host, connectivity and storage
List physical and logical components of hosts Describe key connectivity options Describe the physical disk structure Discuss factors affecting disk drive
performance
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Upon completion of this lesson, you will be able to:
Describe the three components of storage system environment◦ Host, Connectivity and Storage
Detail Host physical and logical components Describe interface protocol
◦ PCI, IDE/ATA and SCSI Describe storage options
◦ Tape, optical and disk drives
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Applications runs on hosts Hosts can range from
simple laptops to complex server clusters
Physical components of host◦ CPU◦ Storage
Disk device and internal memory
◦ I/O device Host to host communications
Network Interface Card (NIC) Host to storage device
communications Host Bus Adapter (HBA)
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LaptopServer
Mainframe
Group of Servers
LAN
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Components of a Host - 6
Speed
Slow
Fast
CostHighLow
TapeOptical
disk
Magnetic disk
RAM
L2 cache L1 cache
CPU registers
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Human interface◦ Keyboard◦ Mouse◦ Monitor
Computer-computer interface◦ Network Interface Card (NIC)
Computer-peripheral interface◦ USB (Universal Serial Bus) port◦ Host Bus Adapter (HBA)
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Components of a Host - 8
Host
Apps
Volume Management
DBMS Mgmt Utilities
File System
Multi-pathing Software
Device Drivers
HBA HBA HBA
Operating System
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Application ◦ Interface between user and the host ◦ Three-tiered architecture
Application UI, computing logic and underlying databases◦ Application data access can be classifies as:
Block-level access: Data stored and retrieved in blocks, specifying the LBA
File-level access: Data stored and retrieved by specifying the name and path of files
Operating system◦ Resides between the applications and the hardware◦ Controls the environment
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Responsible for creating and controlling host level logical storage◦ Physical view of storage is
converted to a logical view by mapping
◦ Logical data blocks are mapped to physical data blocks
Usually offered as part of the operating system or as third party host software
LVM Components:◦ Physical Volumes◦ Volume Groups◦ Logical Volumes
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Physical Storage
Logical Storage
LVM
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One or more Physical Volumes form a Volume Group
LVM manages Volume Groups as a single entity
Physical Volumes can be added and removed from a Volume Group as necessary
Physical Volumes are typically divided into contiguous equal-sized disk blocks
A host will always have at least one disk group for the Operating System◦ Application and Operating
System data maintained in separate volume groups
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Logical Disk Block
Volume Group
Physical Disk Block
Physical Volume 1 Physical Volume 2 Physical Volume 3
Logical Volume
Logical Volume
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Partitioning Concatenation
Logical Volume
Physical Volume
Servers
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Device Drivers◦ Enables operating system to recognize the device ◦ Provides API to access and control devices◦ Hardware dependent and operating system
specific File System
◦ File is a collection of related records or data stored as a unit
◦ File system is hierarchical structure of files Examples: FAT 32, NTFS, UNIX FS and EXT2/3
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UNIX (UFS) File type and permissions Number of links Owner and group IDs Number of bytes in the
file Last file access Last file modification
Windows (NTFS) Time stamp and link
count File name Access rights File data Index information Volume information
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Improves data integrity and system restart time over non-journaling file systems
Uses a separate area called a log or journal◦ May hold all data to be written◦ May hold only metadata
Disadvantage - slower than other file systems◦ Each file system update requires at least 1 extra
write – to the log
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Storage System Environment - 16
1 2 3
456
Consisting of Mapped by LVM to
Teacher (User)Course File(s) File System Files
File System Blocks
LVM Logical Extents
Disk Physical ExtentsDisk Sectors
Configures/Manages
Residing in
Reside in Mapped by a file system to
Managed by disk storage subsystem
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Key points covered in this module: Hosts typically have:
◦ Hardware: CPU, memory, buses, disks, ports, and interfaces
◦ Software: applications, operating systems, file systems, device drivers, volume managers
Journaling enables: ◦ very fast file system checks in the event of system
crash ◦ provides better integrity for file system structure
HBAs are used to connect hosts to storage devices
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Interconnection between hosts or between a host and any storage devices
Physical Components of Connectivity are:◦ Bus, port and cable
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CPU HBA
Port
CableBUS
Disk
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Serial
Serial Bi-directional
Parallel
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System Bus – connects CPU to Memory Local (I/O) Bus – carries data to/from
peripheral devices Bus width measured in bits Bus speed measured in MHz Throughput measured in MB/S
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Protocol = a defined format for communication between sending and receiving devices
◦ Tightly connected entities such as central processor to RAM, or storage buffers to controllers (example PCI)
◦ Directly attached entities connected at moderate distances such as host to storage (example IDE/ATA)
◦ Network connected entities such as networked hosts, NAS or SAN (example SCSI or FC)
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Tightly ConnectedEntities
DirectlyAttachedEntities
Network Connected
Entities
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Host
Apps
Operating System
PCI
SCSI or IDE/ATA Device Drivers
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PCI is used for local bus system within a computer
It is an interconnection between microprocessor and attached devices
Has Plug and Play functionality PCI is 32/64 bit Throughput is 133 MB/sec PCI Express
◦ Enhanced version of PCI bus with higher throughput and clock speed V1: 250MB/s V2: 500 MB/s V3: 1 GB/s
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Integrated Device Electronics (IDE) / Advanced Technology Attachment (ATA)◦ Most popular interface used with modern hard disks◦ Good performance at low cost◦ Inexpensive storage interconnect◦ Used for internal connectivity
Serial Advanced Technology Attachment (SATA)◦ Serial version of the IDE /ATA specification ◦ Hot-pluggable◦ Enhanced version of bus provides upto 6Gb/s
(revision 3.0)
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Parallel SCSI (Small computer system interface)◦ Most popular hard disk interface for servers◦ Supports Plug and Play◦ Higher cost than IDE/ATA◦ Supports multiple simultaneous data access
◦ Used primarily in “higher end” environments ◦ SCSI Ultra provides data transfer speeds of 320
MB/s Serial SCSI
◦ Supports data transfer rate of 3 Gb/s (SAS 300)
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Most popular hard disk interface for servers Higher cost than IDE/ATA Supports multiple simultaneous data access Currently both parallel and serial forms Used primarily in “higher end”
environments
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Target
Initiator
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Target ID
Initiator ID
LUNs
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Initiator ID - a number from 0 to 15 with the most common value being 7.
Target ID - a number from 0 to 15 LUN - a number that specifies a device
addressable through a target.
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Initiator ID Target ID LUN
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Host Addressing◦ Controller◦ Target◦ LUN
Connectivity - 30
c0 – Controller/Initiator/HBA
PeripheralController
t0
Target
LUNs
d0 d1 d2
c0 t0 d0
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Pros:◦ Fast transfer speeds, up to
320 megabytes per second
◦ Reliable, durable components
◦ Can connect many devices with a single bus, more than just HDs
◦ SCSI host cards can be put in almost any system
◦ Full backwards compatibility
Cons:◦ Configuration and setup
specific to one computer◦ Unlike IDE, few BIOS
support the standard◦ Overwhelming number of
variations in the standard, hardware, and connectors
◦ No common software interfaces and protocol
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Connectivity - 32
Feature IDE/ATA SCSI
Connectivity Market Internal Storage Internal and External Storage
Speed (MB/sec) 100/133/150 320
Hot Pluggable No Yes
Expandability Easier to set up Very good but veryexpensive to set up
Cost/Performance Good High cost/Fasttransfer speed
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Bus
Disk
Cable
Host
Port
Port
HBA
CPU
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Connectivity - 34
Fibre Channel
Storage Arrays
Host
AppsDBMS Mgmt Utils
File System
LVM
Multipathing Software
Device Drivers
HBA HBA HBA
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SCSI◦ Limited distance◦ Limited device count◦ Usually limited to single initiator◦ Single-ported drives
Fibre Channel◦ Greater distance◦ High device count in SANs◦ Multiple initiators◦ Dual-ported drives
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iSCSI◦ Transport is over an IP network◦ SCSI Commands are exchanged over an IP
network Fibre Channel over Ethernet
◦ Tunnels fibre channel commands over IP
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Switches Storage
Hosts
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Magnetic Tape◦ Low cost solution for long term data storage◦ Limitations
Sequential data access, Single application access at a time, Physical wear and tear and Storage/retrieval overheads
Optical Disks◦ Popularly used as distribution medium in small, single-
user computing environments◦ Write once and read many (WORM): CD-ROM, DVD-ROM◦ Limited in capacity and speed
Disk Drive◦ Most popular storage medium with large storage capacity◦ Random read/write access
Ideal for performance intensive online application
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Key points covered in this lesson: Host components
◦ Physical and Logical Connectivity options
◦ PCI, IDE/ATA, SCSI Storage options
◦ Tape, optical and disk drive
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Disk drive components, Disk Drive Performance
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Upon completion of this lesson, you will be able to:
List and discuss various disk drive components◦ Platter, spindle, read/write head and actuator arm
assembly Discuss disk drive geometry Describe CHS and LBA addressing scheme Disk drive performance
◦ Seek time, rotational latency and transfer rate Law’s governing disk drive performance Enterprise flash drive
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Interface
Controller
Power Connector
HDA
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Physical Disks - 43
0011010011101010101000110100111010101010
10110101011010101010
01010100111010101010
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Spindle
Platters
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Actuator
Spindle
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Actuator
R/W Head
R/W Head
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Bottom View of Disk Drive
HDA
Controller
Interface
Power Connector
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Sector
Track
Platter
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Platter Without Zones
Sector
Track
Platter With Zones
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Cylinder
Tracks, Cylinders and Sectors
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Physical Address = CHS Logical Block Address = Block #
Sector
CylinderHead
Block 0
Block 16
Block 32
Block 48
Block 8
(lower surface)
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A
Concatenation -
One Logical Volume
Partitioning -
Multiple Logical Volumes
ABC
D
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Key points covered in this lesson: Physical drives are made up of:
◦ HDA Platters connected via a spindle Read/write heads which are positioned by an actuator
◦ Controller Controls power, communication, positioning, and
optimization Data is structured on a drive using tracks,
sectors, and cylinders The geometry of a disk impacts how data is
recorded on a platter
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Disk Drive Performance Logical Components
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Upon completion of this lesson, you will be able to:
Describe the factors that impact the performance of a drive
Describe how drive reliability is measured
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Seek time is the time for read/write heads to move between tracks
Seek time specifications include:◦ Full stroke◦ Average◦ Track-to-track
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Physical Disks - 59
Request 1
Request 2
Request 3
Request 4
1234
Request 1
Request 2
Request 3
Request 4
1324
Without Command Queuing
With Command Queuing
1
2
34
1
2
34
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InterfaceInterface BufferBufferHBAHBA
Disk Drive
Internal transfer rate measured here
External transfer rate measured here
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Mean Time Between Failure Amount of time that one can anticipate a
device to work before an incapacitating malfunction occurs◦ Based on averages◦ Measured in hours
Determined by artificially aging the product
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Consider a disk I/O system in which an I/O request arrives at a rate of 100 I/Os per second. The service time, RS, is 4 ms. ◦ Utilization of I/O controller (U=a × Rs) ◦ Total response time (R=Rs /1-U)
Calculate the same with service time is doubled
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0% 100%Utilization
Knee of curve: disks at
about 70% utilization
Low Queue Size
70%
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Conventional disk drive Mechanical Delay associated
with conventional drive◦ Seek time ◦ Rotational latency
More power consumption due to mechanical operations
Low Mean Time Between Failure
Enterprise flash drive Highest possible throughput
per drive◦ No Spinning magnetic media◦ No Mechanical movement
which causes seek and latency
◦ Solid State enables consistent I/O performance
Very low latency per I/O Energy efficient storage
design◦ Lower power requirement per
GB of storage◦ Lower power requirement per
IOPS
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Drive is based on Flash Solid State memory technology◦ High performance and low latency ◦ Non volatile memory◦ Uses single layer cell (SLC) or Multi Level cell (MLC)
to store data Enterprise Flash Drives use a 4Gb FC interface
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Faster performance◦ Up to 30 times greater
IOPS (benchmarked)◦ Typical applications: 8 –
12X◦ Less than 1 millisecond
service time More energy efficient
◦ 38 percent less per terabyte
◦ 98 percent less per IO Better reliability
◦ No moving parts◦ Faster RAID rebuilds
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IO per secondR
esp
on
se T
ime
1 Flash drive
1@15K FibreChannel drive
10@15K Fibre Channeldrives
30@15KFibre
Channel drives
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Position Enterprise Flash Drives as the high-performance option in demanding environments◦Low latency applications, also known as “Tier-0”
applications Standard form-factor and capacity design allows
for easier integration High performance, low power for a “Green”
initiative Target Customer/Market Segments:
◦ High performance solutions coupled with low power◦ Specifically target Oracle database customers initially◦ Financial trading◦ OLTP databases
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Key points covered in this lesson: Disk drive components and geometry Disk drive addressing scheme Disk drive performance Convention drive Vs Enterprise Flash Drives Enterprise Flash Drives for high
performance and low power storage solution
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Key points covered in this chapter: Storage system environment components:
◦ Host, connectivity and storage Physical disk structure and addressing Factors affecting disk performance Flash drives benefits
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What are some examples of hosts? What are the physical and logical
components of a host? What are the common connectivity
protocols used in computing environments? What is the difference between seek time
and rotational latency? What is the difference between internal and
external data transfer rates?
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