TOPIC SEVEN

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• TOPIC SEVEN
• Disk and Backup Technology
• Hard Disk Subsystems
• SSDs Solid State Disks
• George South

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• 7.1 Hard Disk Subsystems
• The hard disk subsystem of a PC is an important
  element of the configuration
• However for office/ work station applications it
  requires less technical consideration than in the
  past
• This is because large, fast disk systems are now
  relatively cheap and the performance of such
  systems does not significantly affect the
  ultimate performance of the PC
• This is particularly true for applications, which
  are mainly memory based
• Some PCs now use a combination of hard and solid
  state disks giving performance and large storage

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•  7.1.1 Exercise List FIVE PC activities which
  will
• benefit from a fast disk drive
• Compiling a C program which uses the disk drive
  to store temporary files
• Compressing a video using a codec
• Accessing a complex database
• Loading and using a complex application
  especially where the help files are large and on
  the disk
• Scanning for Viruses, Spyware, Malware etc
• Searching for a lost file
• Booting up

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•  7.1.2 Exercise List FIVE PC activities which
• will not benefit from a fast disk drive
  
• Surfing the Internet (although visited web pages
  are stored in a disk based cache memory)
• Low performance Office applications such as Word
• Developing web pages
• Running a video conferencing tool
• Accessing simple email

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7.1.3 Exercise Until recently the usual
desktop standard was called ATA 100 or
133Describe the features of such disk drives

• 1. ATA stands for AT Attachment
• 2. It comes from the time when the hard disk
  interfaced to a PC using the AT (later called the
  ISA) bus
• 3. Although the AT bus is no longer used, an ATA
  disk drive still mimics this interface
• 4. The 100 or 133 indicates the maximum data rate
  e.g. 100 Mbytes/second

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• 7.1.5 A typical EIDE disk subsystem has the
  following specification
•       access time 9 ms
•       data buffer size 16 MByte
•       spin speed 7,200 RPM
•       size 500 GByte
•       cost 60 pounds
•  
• What does EIDE stand for ?
• Why does the data buffer improve the performance
  ?
• Avoids writing on a byte by byte basis to the
  disk disk transfers occur in efficient blocks
  it is a disk cache

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• 7.2 SELECTING THE DISK SIZE
•  
• The usual advice is to the buy the largest disk
  drive that your budget can afford
• SATA Hard disk drives are cheap
• Historically new versions of software packages
  are considerably larger than previous versions
  and the extra storage will soon get used up
• A high resolution image say 12 Mega -pixels and
  32-bit colour would require 36 MBytes storage
• Video storage requirements are much greater

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•  7.3 Serial ATA
• The latest systems support Serial ATA
• 7.3.1 Exercise Justify the features of SATA
• Parallel connections such as ATA to IDE drives
  cannot transmit data any faster than about 100
  MBytes/sec because of problems such as cross-talk
• The solution is to use a carefully designed high
  performance serial interfaces
• The IDE drive technology doesnt need to change,
  but the interface is now serial

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•  
• 7.3.2 Serial ATA - NCQ
• SATA also allows disk drives to become smarter
• Intelligent Seeking or Native Command Queuing is
  a technology designed to increase performance of
  SATA hard disks it allows the disk firmware to
  internally optimise the order in which read and
  write commands are executed
• This can result in increased performance
  depending on the application
• Notes

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• 7.3.3 A PC using Serial ATA - picture

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•  
• 7.3.4 A PC using Serial ATA - diagram

SATA cable
EIDE Drive
Motherboard
SATA interface
SATA interface
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7.3.5 From the SATA web site

• Serial ATA was introduced at 1500 Mbps, with a
  roadmap planned to 6000 Mbps, supporting up to 10
  years of storage evolution based on historical
  trends
• Serial ATA is fully compliant with the ATA
  protocol and thus is software compatible
• Ref http//www.serialata.org/satatechnology.asp
• The terminology is not to use SATA Version 1 etc
  but to quote the max data rate e.g. SATA 1.5
  Gbit/s, SATA 3.0 Gbit/s

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• 7.4 SCSI DISK DRIVES
•  
• More demanding applications use SCSI drives which
  are sometimes larger and faster but significantly
  more expensive
• These drives are more reliable than SATA drives
•  
• SCSI stands for .. Small Computer System
  Interface

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• A typical SCSI disk subsystem has the following
  specification
•  
•       access time 6 ms
•       data buffer size 4 MByte
•       spin speed 10000 RPM
•       size 73.4 GB
•       cost 200 pounds
• Comments
• -The latest version of SCSI uses a serial
  interface and is called SAS Serial Attached SCSI
• -Faster and more expensive than SATA
• -The interface is very similar to SATA

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State two applications which would benefit from
using the features of SAS drives

• Graphics Workstation
• Server
• Notes
• These often run tasks which can benefit from high
  performance peripherals
• The extra cost of a SAS system can be justified
• Traditionally SCSI drives are more reliable

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7.5 Conventional disk drives are
electromechanical SSDs Solid State Drives are
more robust

• Solid State Drives are made from Flash RAM (as
  used in memory sticks)
• SSDs feature low power, low weight, fast access
  etc - ideal for mobile PCs e.g. laptops
• The major problem is cost !!!
• The smallest useful SSD solid state drive is 2 GB
  as used in Ultra Mobile PCS the cost of 4 GB of
  Flash RAM is about 10 pounds (2.5 pounds/ GByte)
• Compare with a 500 GB hard drive at 50 pounds or
  (10 p/ GByte)
• the SSD equivalent is 1250 pounds !!

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Turbo Memory

• Intel have proposed a method of reducing the
  number of accesses to disk
• The idea is to add a Flash memory module to the
  motherboard see P35 chipset diagram
• Software will use this as a cache, so before
  accessing the disk, the operating system looks
  in this cache (so called Turbo Memory)
• Advantages
• Disadvantages -

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Tutorial on Topic SevenDisk and Backup
Technology http//video.intel.com/?fr_story4860
a526df90396d7fc77e1cca092d8ae8d43226rfbm
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Use a table to compare the features of SATA, SAS
and Solid State Drives
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Compare the technologies available for connecting
external disk drives

• eSATA i/f at least 1.5 Gbps
• ! 2 metre cable max
• ! Not featured on most PCs
• USB USB2.0 up to 480 Mbps
• most PCs and laptops
• 5 volts at 0.5 Amps now USB3.0
• Firewire e.g. 800 Mbps
• ! Not implemented on many PCs
• Conclusion USB very popular

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Compare the cost per MByte for typical storage
media

• List the media Hard Disk, SSD, USB Flash Memory
  Drive, Tape, CD
• State typical storage and price
• Hard Disk 500 GByte/ 50 10 GB/1
• SSD 128 GB / 350 about 0.4 GB/ 1
• USB Flash 4 GB/ 10 about 0.4 GB/ 1
• CD/DVD 5 GB/ 1
• Tape 40 GB/ 10 4 GB/ 1

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Describe the boot up sequence of a PC

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Describe the boot up sequence of a PC

• PC is powered up and processor starts executing
  BIOS code at address FFFF0H
• BIOS performs some basic tests of the hardware
  called POST Power On Self Test
• BIOS looks for video card and video BIOS
• BIOS looks for hard disk controller and ATA BIOS
• Memory is tested
• Plug and Play devices are configured
• BIOS searches for boot device e.g. Hard Disk C
• The processor executes the code in the Master
  Boot Record
• The partition information is read which
  identifies say a dual boot the user is prompted
• A Loader program for the selected OS executes
• The OS is loaded and control is passed to it

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PCIe x16
Core i3, i5, i7
PCIe x1
SATA eSATA
Smart Storage
Q57 for Professional Market
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(No Transcript)
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Compare the cost per MByte for Typical storage
media
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A disk is formatted what does this mean ?

• To prepare a disk, for reading and writing
• When you format a disk, the operating system
  erases all bookkeeping information on the disk,
  tests the disk to make sure all sectors are
  reliable, marks bad sectors (that is, those that
  are scratched), and creates internal address
  tables that it later uses to locate information
• A disk must be formatted before use
• Ref http//www.webopedia.com/TERM/f/format.html

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Windows supplies a utility to de-fragment a disk
why do this ?

• Refers to the condition of a disk in which files
  are divided into pieces scattered around the
  disk.
• Fragmentation occurs naturally when you use a
  disk frequently, creating, deleting, and
  modifying files.
• At some point, the operating system needs to
  store parts of a file in non-contiguous clusters.
  
• This is entirely invisible to users, but it can
  slow down the speed at which data is accessed
  because the disk drive must search through
  different parts of the disk to put together a
  single file.
• Ref http//www.webopedia.com/TERM/f/fragmentation.
  html

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Describe the boot up sequence of a PC

• PC is powered up and processor starts executing
  BIOS code at address FFFF0H
• BIOS performs some basic tests of the hardware
  called POST Power On Self Test
• BIOS looks for video card and video BIOS
• BIOS looks for hard disk controller and ATA BIOS
• Memory is tested
• Plug and Play devices are configured
• BIOS searches for boot device e.g. Hard Disk C
• The processor executes the code in the Master
  Boot Record
• The partition information is read which
  identifies say a dual boot the user is prompted
• A Loader program for the selected OS executes
• The OS is loaded and control is passed to it

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Compare the cost per MByte for typical storage
media

• List the media Hard Disk, Floppy Disk, USB
  Flash Memory Drive, Tape, CD
• State typical storage and price
• Hard Disk 80 GByte 80 pounds 1 GB/pound
• Floppy Disk 1 MB 20 pence 5 MB/ pound
• USB Flash 256 MB 25 pounds 10 MB/ pound
• Tape 20 GB 5 pound 4 GB / pound
• CD 500 MB 50 pence 1 GB /pound

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Why use dual booting ?

• It is possible to run several OS systems on a PC
  but only one at a time
• Some packages are written for a specific OS e.g.
  Windows NT
• In our labs we sometimes use a dual boot to allow
  older packages to run under say Windows NT but
  user a more modern version of Windows for other
  packages

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1. Original PC with a hard drive
C Hard Disk
Disk Interface
8088 processor
A Floppy Disk
IBM PC-XT motherboard
PC bus
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2. Early IDE Disk Drives
ATA cable
Passive connector
IDE Disk Drive
386/486 Era PC
ISA (AT) bus
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• 3. ATA Disk Drives using Parallel ATA    
•  

Modern PC with ATA integrated into chip set
S P
AGP bus PCI bus
cable
Primary and Secondary ATA interfaces
Hard Disk or CDROM Drive
IDE Disk Interface
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• 4. ATA Disk Drives using Serial ATA    
•  

Modern PC with ATA integrated into chip set

PCIe bus PCI bus
SATA cable
4 SATA channels only 1 used here
Hard Disk
IDE Disk Interface
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•  
• Terms (defined by the Small Form Factor (SFF)
  Committee
•  
• Attachment (ATA) standard used to define IDE and
  EIDE interfaces
• AT Packet Interface (ATAPI) is an extension to
  the ATA standard for non-hard disk devices e.g.
  CD-ROMs
•  

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• Configuration
• note
• if you have an ATA 100 EIDE controller and an ATA
  100 hard drive
• don't add a ATA 33 device such as a CD-ROM drive
  to the channel
• it will work at 8.33 MHz.. place the CD-ROM on
  the second EIDE channel
•  

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• 7.1.4 Exercise Draw a diagram showing the
  conventional ATA Primary and Secondary channels
  on a legacy PC motherboard   

The Intel P35 chipset only provides no Parallel
ATA channels
Graphics bus PCI bus
Modern PC with ATA integrated into chip set
S P
cable
Primary and Secondary ATA interfaces
Hard Disk or CDROM Drive
IDE Disk Interface