ISDMR:BEIT VIII: CHAP2:MADHU N 1 ISM - Course Organization.

ISDMR:BEIT VIII: CHAP2:MADHU N

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ISM - Course OrganizationInformation Storage

and Management

Section 1

Storage System

Section 2

Storage Networking

Technologies and Virtualization

Section 3

Business Continuity

Section 4

Storage Security

and Management

Introduction to Information

Storage and Management

Storage System Environment

Data Protection: RAID

Intelligent Storage System

Direct-Attached Storage and

Introduction to SCSI

Storage Area Networks

Network-Attached Storage

IP SAN

Content-Addressed Storage

Storage Virtualization

Introduction to

Business Continuity

Backup and Recovery

Local Replication

Remote Replication

Securing the

Storage Infrastructure

Managing the

Storage Infrastructure


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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


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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)

LaptopServer

Mainframe

Group of Servers

LAN


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Host: Logical Components

Host

DBMS

HBA HBA HBA

Applications

Volume Manager

Operating System

File System

Device Drivers


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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 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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Logical Components of the Host: LVM

• 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– Application and Operating

System data maintained in separate volume groups

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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LVM Example: Partitioning and Concatenation

Partitioning Concatenation

Logical Volume

Physical Volume

Servers


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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


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How Files are Moved to and from Storage

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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Connectivity

• Interconnection between hosts or between a host and any storage devices

• Physical Components of Connectivity are:– Bus, port and cable

CPU HBA

Port

CableBUS

Disk


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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)

– Network connected entities such as networked hosts, NAS or SAN (example SCSI or FC)

Tightly ConnectedEntities

DirectlyAttachedEntities

Network Connected

Entities


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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 is 32/64 bit• Throughput is 133 MB/sec• PCI Express

– Enhanced version of PCI bus with higher throughput and clock speed


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Popular Connectivity Options: IDE/ATA

• 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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Popular Connectivity Options: SCSI

• 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 – 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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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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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


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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

HDA


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Physical Disk Structure

Sector

Track

Platter

SectorTrack

Cylinder

Spindle


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Logical Block Addressing

Physical Address= CHS

Cylinder 2

Head 0

Sector 10

Block 48

Block 16

Block 32

Logical Block Address= Block#

Block 0

Block 8

(Upper Surface)

(Lower Surface)


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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)


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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


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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 15000-

rpm drive


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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

InterfaceInterface BufferBufferHBAHBA

Disk Drive

Internal transfer rate measured here

External transfer rate measured here

Head Disk AssemblyHead Disk Assembly


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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 time126 5 4 3

I/O

ControllerProcessed I/O Request

ArrivalI/O Queue


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Utilization vs. Response time

• 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

0% 100%Utilization

Knee of curve: disks at

about 70% utilization

Low Queue Size

70%


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Enterprise Flash Drives: A New Generation DrivesConventional 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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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


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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 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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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


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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


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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 + 4K/40MB = 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)


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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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Check Your Knowledge

• 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?

ISDMR:BEIT VIII: CHAP2:MADHU N 1 ISM - Course Organization.

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