Hard Drives Non-Volatile Storage. Hard Drives Hard Drives (HD) The primary storage device in a...

Hard DrivesHard Drives

Non-Volatile StorageNon-Volatile Storage


Hard Drives (HD)Hard Drives (HD)

The primary storage device in a The primary storage device in a computer systemcomputer system


Invented in 1950’sInvented in 1950’s

Also called:Also called:

Fixed DisksFixed Disks

Hard DisksHard Disks

Primary StoragePrimary Storage


Common Capacities:Common Capacities:

20 GB 30 GB 40 GB20 GB 30 GB 40 GB

60 GB 80 GB 100 GB60 GB 80 GB 100 GB

120 GB 160 GB 200 GB 300 GB120 GB 160 GB 200 GB 300 GB

400 GB 500 GB400 GB 500 GB


Data is stored as FilesData is stored as Files

Files are collections of BytesFiles are collections of Bytes


Files are simply strings of bytes Files are simply strings of bytes stored on the hard drivestored on the hard drive


Files are fetched into Memory by Files are fetched into Memory by the CPU one byte at a time, and the CPU one byte at a time, and

stored on the HD one byte at a timestored on the HD one byte at a time


The time to retrieve data is The time to retrieve data is measured in two ways:measured in two ways:

Data RateData Rate

Seek TimeSeek Time


Data Rate:Data Rate:

The data rate is the number of The data rate is the number of bytes per second that the drive can bytes per second that the drive can deliver to the CPU. Rates between deliver to the CPU. Rates between 5 and 160 megabytes per second 5 and 160 megabytes per second

are common. are common.


Seek Time:Seek Time:

The seek time is the amount of time The seek time is the amount of time between when the CPU requests a between when the CPU requests a file and when the first byte of the file file and when the first byte of the file is sent to the CPU. Times between is sent to the CPU. Times between 8 and 20 milliseconds are common.8 and 20 milliseconds are common.


View of aView of a

TypicalTypical

Internal Internal Hard DriveHard Drive


Inside aInside a

Hard DriveHard Drive


Platters:Platters:

Typically spin at 3,600 to 10,000 Typically spin at 3,600 to 10,000 RPM when the drive is operating. RPM when the drive is operating. These platters are manufactured These platters are manufactured

to amazing tolerances and are to amazing tolerances and are mirror-smooth.mirror-smooth.


Read/Write Read/Write HeadsHeads

PlattersPlatters


Data is stored on the surface of a Data is stored on the surface of a platter in platter in sectorssectors and and trackstracks. .


Tracks Tracks are are concentric circlesconcentric circles

(Yellow)(Yellow)

SectorsSectors are pie- are pie-shaped wedges on shaped wedges on

a tracka track(Blue)(Blue)


Low-Level formatting a drive Low-Level formatting a drive establishes the tracks and sectors establishes the tracks and sectors

on the platter.on the platter.


Partitioning a Hard DrivePartitioning a Hard Drive

Separates the Hard Drive into Separates the Hard Drive into Logical PiecesLogical Pieces


Partitioning a Hard DrivePartitioning a Hard Drive

Drive C: Drive C:

is always the first Logical drive is always the first Logical drive partition of the first Hard Drive partition of the first Hard Drive

registered in the systemregistered in the system

Hard DrivesHard DrivesPartitioning Example:Partitioning Example:

80 GB

One Primary Partition

Drive C:

Hard DrivesHard DrivesPartitioning Example:Partitioning Example:

20 GB 20 GB 20 GB 20 GB

Primary

C:

Logical

D:

Logical

E:

Logical

F:


High-level formatting writes the file-High-level formatting writes the file-storage structures, like the file-storage structures, like the file-

allocation table, into the sectors. allocation table, into the sectors. This process prepares the drive to This process prepares the drive to

hold files. hold files.


Head CrashHead Crash

Causes Physical Damage to the Causes Physical Damage to the Hard Drive PlattersHard Drive Platters

CatastrophicCatastrophic

Data Not Usually RecoverableData Not Usually Recoverable

End of SectionEnd of Section


Fragmentation of Hard DriveFragmentation of Hard Drive

Defragmentation of Hard DriveDefragmentation of Hard Drive


Fragmentation of Hard DriveFragmentation of Hard Drive

Occurs as files are written to the Occurs as files are written to the hard drive during normal operationhard drive during normal operation

Files are written out of consecutive Files are written out of consecutive orderorder


Defragmentation of Hard DriveDefragmentation of Hard Drive

Resetting the files back in Resetting the files back in consecutive order on the Hard Driveconsecutive order on the Hard Drive

Via a Defrag ProgramVia a Defrag Program


Hard Drive ManufacturersHard Drive Manufacturers

MaxtorMaxtor

SeagateSeagate

Western DigitalWestern Digital

FujitisuFujitisu

SamsungSamsung


Hard Drive TypesHard Drive Types

IDEIDE

SCSISCSI

USBUSB

FIREWIREFIREWIRE


IDEIDE

Integrated Drive Electronics Integrated Drive Electronics

5400 – 7200 RPM5400 – 7200 RPM

ATA-100/133 MB/SecATA-100/133 MB/Sec

UDMA-5UDMA-5


Cable Types:Cable Types:

IDEIDE

40/50 Pin & 40/50 Pin &

80 Pin80 Pin


SCSISCSI

Small Computer System Interface Small Computer System Interface 5400 – 10,000 RPM5400 – 10,000 RPM

SCSI, SCSI-2, SCSI-3SCSI, SCSI-2, SCSI-3

Ultra-SCSI, Ultra-Wide SCSI,Ultra-SCSI, Ultra-Wide SCSI,

Ultra-160 SCSI, Ultra-320 SCSIUltra-160 SCSI, Ultra-320 SCSI


Cable Types:Cable Types:

SCSISCSI

(Over 20 Connection Types)(Over 20 Connection Types)


RAIDRAID

RRedundant edundant AArray of rray of IIndependent ndependent DDisksisks


RAID LevelsRAID Levels

Level 0:Level 0:

Provides Provides Data StripingData Striping



Level 1:Level 1:

Provides Disk Mirroring Provides Disk Mirroring



Level 0 + 1Level 0 + 1

Combines both Data Stripping and Combines both Data Stripping and Data MirroringData Mirroring



Level 5:Level 5:

Provides data striping at the byte Provides data striping at the byte level and also stripe error correction level and also stripe error correction information. This results in excellent information. This results in excellent

performance and good fault performance and good fault tolerance. tolerance.


STRIPPINGSTRIPPING

Requires at least 2 HDs to workRequires at least 2 HDs to work

Should be same type, speed, sizeShould be same type, speed, size


MirroringMirroring

Requires at least 2 HDs to workRequires at least 2 HDs to work

Should be same type, speed, sizeShould be same type, speed, size


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