1. Storage System Environment
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Section 1 : Storage System
Storage System Environment
Chapter 2

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Chapter Objectives
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

3. Lesson: Components of Storage System Environment
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Lesson: Components of Storage System Environment
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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Host
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)
Server
Laptop
Group of Servers
LAN
Mainframe

5. Host: Logical Components
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Host: Logical Components
Host
DBMS
HBA
Applications
Volume Manager
Operating System
File System
Device Drivers

6. Logical Components of the Host
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Logical Components of the Host
Application
Interface between user and the host
Three-tiered architecture
Application UI, computing logic and underlying databases
Application data access can be classified as:
Block-level access: Data stored and retrieved in blocks, specifying the LBA (logical block address)
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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Quiz Question
Which statements is true?
File-level access is a data stored and retrieved by specifying the name and path of files
Applications runs on device manager
Block-level access is a data stored and retrieved in blocks, specifying the logical block address
File systems are resides between the applications and the hardware

8. Logical Components of the Host: LVM (Logical Volume Manager)
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Logical Components of the Host: LVM (Logical Volume Manager)
Provides a method for allocating space on mass-storage devices that is more flexible than conventional partitioning schemes.
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
Physical Storage
Logical Storage
LVM

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Volume Groups
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
Usually, Application and Operating System data is maintained in separate volume groups
Logical Volume
Logical Disk Block
Logical Volume
Physical Volume 1
Physical Volume 2
Physical Volume 3
Physical Disk Block
Volume Group

10. LVM Example: Partitioning and Concatenation
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LVM Example: Partitioning and Concatenation
Servers
Logical Volume
Physical Volume
Partitioning
Concatenation

11. Logical Components of the Host (Cont)
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Logical Components of the Host (Cont)
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 EXT2/3/4
Additional Task
Research on Blade Server
Technology & File Systems

12. How Files are Moved to and from Storage
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How Files are Moved to and from Storage 1 2 3 4 5 6
Consisting of
Mapped by
LVM to
Teacher (User)
Course File(s)
File System Files
File System
Blocks
LVM Logical Extents
Disk Physical
Extents
Disk Sectors
Configures/
Manages
Residing in
Reside in
Mapped by a file
system to
Managed by
disk storage
subsystem

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Connectivity
Interconnection between hosts or between a host and any storage devices
Physical Components of Connectivity are:
Bus, port and cable
CPU
HBA
Port
Cable
BUS
Disk

14. Connectivity Protocol
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Connectivity Protocol
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/SATA)
Network connected entities such as networked hosts, NAS or SAN (example SCSI or FC)
Tightly Connected Entities
Directly Attached Entities
Network Connected Entities

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Quiz Question
What is the use of Logical Volume Manager?
Interconnection between hosts or between a host and any storage devices
Tightly connected entities such as central processor to RAM, or storage buffers to controllers
Responsible for creating and controlling host level logical storage
Enables operating system to recognize the device

16. Popular Connectivity Options: PCI
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Popular Connectivity Options: PCI
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 can support both 32-bit and 64-bit data bus
Throughput depends on size of data bus and signal frequency:
133 MBps (32-bit at 33MHz)
266 MBps (32-bit at 66 MHz or 64-bit at 33 MHz)
533 MBps (64-bit at 66 MHz)
PCI Express (PCIe)
Enhanced version of PCI bus with higher throughput and clock speed
Commonly used for graphics card

17. Popular Connectivity Options: IDE/ATA/SATA
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Popular Connectivity Options: IDE/ATA/SATA
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
Has replaced ATA/IDE in most computers nowadays
Hot-pluggable

18. Popular Connectivity Options: SCSI/SAS
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Popular Connectivity Options: SCSI/SAS
Parallel SCSI (Small computer system interface)
Most popular hard disk interface for servers
Higher cost than IDE/ATA
Supports multiple simultaneous data access
Used primarily in “higher end” environments
Serial SCSI (SAS)
Cheaper, simpler and provides higher performance than parallel SCSI
Replaces parallel SCSI in servers nowadays

19. Storage: Medias and Options
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Storage: Medias and Options
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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Quiz Question
What is the use of Logical Volume Manager?
Interconnection between hosts or between a host and any storage devices
Tightly connected entities such as central processor to RAM, or storage buffers to controllers
Responsible for creating and controlling host level logical storage
Enables operating system to recognize the device

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Lesson Summary
Key points covered in this lesson:
Host components
Physical and Logical
Connectivity options
PCI, IDE/ATA, SCSI
Storage options
Tape, optical and disk drive
Additional Task
Research on various media
technologies & their performance

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Lesson: Disk Drive
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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Disk Drive Components
Interface
Controller
Power
Connector
HDD

24. Physical Disk Structure
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Physical Disk Structure
Spindle
Sector
Track
Sector
Cylinder
Track
Platter

25. Physical Disk Structure
Data is recorded on tracks
Concentric rings on the platter around the spindle
Tracks are numbered, starting from 0, from the outer edge of the platter
Track density measures how tightly the tracks are packed
There are thousands of tracks on a single platter
Tracks are divided into smaller units called sectors
Most modern hard drives have 63 sectors per track
A sector typically holds 512 bytes
A cylinder is a set of identical tracks on both surfaces of each drive platter
Location of drive head is referred to by cylinder number

26. Logical Block Addressing
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Logical Block Addressing
Sector 10
Block 48
Block 16
Block 32
Logical Block Address= Block#
Block 0
Block 8
(Upper Surface)
(Lower Surface)
Head 0
Cylinder 2
Physical Address= CHS

27. Logical Block Addressing
Earlier drives use physical address consisting of cylinder, head and sector (CHS)
OS needs to be aware of disk geometry
Logical block addressing (LBA) simplifies the disk addressing by using a linear address to access the physical blocks
The disk controller translates LBA to CHS address
OS only needs to know the number of blocks available
Example 1: Say that a disk 8 sectors per track, 8 heads and 4 cylinders. In total, how many blocks are available?
Example 2: If a sector holds 512 bytes, how many blocks are required for a 500GB hard disk?

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Quiz Question
What is the use of Logical Volume Manager?
Interconnection between hosts or between a host and any storage devices
Tightly connected entities such as central processor to RAM, or storage buffers to controllers
Responsible for creating and controlling host level logical storage
Enables operating system to recognize the device

29. Disk Drive Performance
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Disk Drive Performance
Electromechanical device
Impacts the overall performance of the storage system
Disk Service Time
Time taken by a disk to complete an I/O request
Seek Time
Rotational Latency
Data Transfer Rate
Disk service time =
Seek time + (rotational delay/speed in RPM)+ (block size/transfer rate)

30. Disk Drive Performance: Seek Time
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Disk Drive Performance: Seek Time
Time taken to position the read/write head
Lower the seek time, the faster the I/O operation
Seek time specifications include:
Full stroke
Average
Track-to-track

31. Disk Drive Performance: Rotational Speed/Latency
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Disk Drive Performance: Rotational Speed/Latency
The time taken by platter to rotate and position the data under the R/W head
Depends on the rotation speed of the spindle
Average rotational latency
One-half of the time taken for a full rotation
Appx. 5.5 ms for 5400-rpm drive
Appx. 2.0 ms for rpm drive

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Quiz Question
What is the use of Logical Volume Manager?
Interconnection between hosts or between a host and any storage devices
Tightly connected entities such as central processor to RAM, or storage buffers to controllers
Responsible for creating and controlling host level logical storage
Enables operating system to recognize the device

33. Disk Drive Performance: Data Transfer Rate
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Disk Drive Performance: Data Transfer Rate
Average amount of data per unit time
Internal Transfer Rate
Speed at which data moves from a track to disk internal buffer
External Transfer Rate
The advertised speed of the interface
External transfer rate measured here
Internal transfer rate measured here
Buffer
HBA
Interface
Head Disk Assembly
Disk Drive

34. Fundamental Laws Governing Disk Performance
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Fundamental Laws Governing Disk Performance
Little’s Law
Describes the relationship between the number of requests in a queue and the response time.
N = a × R
“N” is the total number of requests in the system
“a” is the arrival rate
“R” is the average response time
Utilization law
Defines the I/O controller utilization
U = a × Rs
“U” is the I/O controller utilization
“Rs“ is the service time 1 2 6 5 4 3
I/O
Controller
Processed I/O Request
Arrival
I/O Queue

35. Fundamental Laws Governing Disk Performance
Average inter-arrival time, Ra = 1 / a
Average time between the arrival of the current I/O request to the arrival of the next I/O request
Total response time, R = Rs / (1 – U)
The time between the request arrival until the completion of I/O process
Average queue size = U2 / (1 – U)
Time spent by a request in queue = U x R

36. Utilization vs. Response time
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Utilization vs. Response time
Knee of curve: disks at
about 70% utilization
Low Queue Size 0%
Utilization
70%
100%
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
Additional Task
Research on Disc Drive Technology

37. Application Requirements and Disk Performance
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Application Requirements and Disk Performance
Exercise:
Consider an application that requires 1TB of storage capacity and performs 4900 IOPS
Application I/O size is 4KB
As it is business critical application, response time must be within acceptable range
Specification of available disk drive:
Drive capacity = 73 GB
15000 RPM
5 ms average seek time
40 MB/sec transfer rate
Calculate the number of disks required?

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Solution
Calculate time required to perform one I/O
=Seek time + (rotational delay/speed in RPM)+ (block size/transfer rate)
Therefore, 5 ms + (0.5/15000) + 4KB/(40MB/s) = 7.1 msec
Calculate max. number of IOPS a disk can perform
1 / 7.1 ms = 140 IOPS
For acceptable response time disk controller utilization must be less than 70%
Therefore, 140 X 0.7 = 98 IOPS
To meet application
Performance requirement we need 4900/98 i.e. 50 disk
Capacity requirement we need 1TB/ 73 GB i.e. 14 disk
Disk required = max (capacity, performance)

39. Application Requirements and Disk Performance
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Application Requirements and Disk Performance
Exercise:
Consider an application that requires 2TB of storage capacity and performs 2600 IOPS
Application I/O size is 2KB
Specification of available disk drive:
Drive capacity = 200GB
12000 RPM
5 ms average seek time
40 MB/sec transfer rate
Calculate the number of disks required?

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Quiz Question
What is the use of Logical Volume Manager?
Interconnection between hosts or between a host and any storage devices
Tightly connected entities such as central processor to RAM, or storage buffers to controllers
Responsible for creating and controlling host level logical storage
Enables operating system to recognize the device

41. Enterprise Flash Drives: A New Generation Drives
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Enterprise Flash Drives: A New Generation Drives
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

42. Enterprise Flash Drives – Overview
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Enterprise Flash Drives – Overview
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

43. Enterprise Flash Drives – Benefits
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Enterprise Flash Drives – Benefits
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
IO per second
Response Time
1 Flash drive
Fibre Channel drive
Fibre Channel drives
Fibre Channel drives

44. Enterprise Flash Drives – “Tier-0” Application
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Enterprise Flash Drives – “Tier-0” Application
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
Additional Task
Research on Flash Drive
Technology

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Lesson Summary
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

46. Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved.
Chapter Summary
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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