Title: TOPIC SEVEN
1- TOPIC SEVEN
- Disk and Backup Technology
- Hard Disk Subsystems
- SSDs Solid State Disks
- George South
2- 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
3- 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
4- 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
57.1.3 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
6- 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
7- 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
8- 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
9-
- 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
10- 7.3.3 A PC using Serial ATA - picture
11-
- 7.3.4 A PC using Serial ATA - diagram
SATA cable
EIDE Drive
Motherboard
SATA interface
SATA interface
127.3.5 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
13- 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
14- 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
15State 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
167.5 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 !!
17Turbo 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 -
18Tutorial on Topic SevenDisk and Backup
Technology http//video.intel.com/?fr_story4860
a526df90396d7fc77e1cca092d8ae8d43226rfbm
19Use a table to compare the features of SATA, SAS
and Solid State Drives
20Compare 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
21Compare 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
22Describe the boot up sequence of a PC
23Describe 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
24PCIe x16
Core i3, i5, i7
PCIe x1
SATA eSATA
Smart Storage
Q57 for Professional Market
25(No Transcript)
26Compare the cost per MByte for Typical storage
media
27A 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
28Windows 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
29Describe 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
30Compare 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
31Why 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
321. Original PC with a hard drive
C Hard Disk
Disk Interface
8088 processor
A Floppy Disk
IBM PC-XT motherboard
PC bus
332. Early IDE Disk Drives
ATA cable
Passive connector
IDE Disk Drive
386/486 Era PC
ISA (AT) bus
34- 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
35- 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
36-
- 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 -
37- 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 -
38- 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