Chpt6 Storage - Hard Disk Drive

8/9/2019 Chpt6 Storage - Hard Disk Drive

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A+ Certification for PC Technician

Chapter 6Chapter 6Storage - Hard Disk Drive


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Slide 2Ver 1.0 10 April 2001

Hard DiskHard Disk

What is the role of the Hard Disk?It is Permanent Storage device in thePC. It is the computers PrimaryStorage

How is the Hard Disk differ from otherstorage device?

Storage Capacity and Speed.

How is Capacity measured?

Megabyte (MB) for older Hard diskGigabyte (GB) for newer hard disk

How is Hard Disk measured?

The speed of the hard disk aremeasured in term of Data Access Time(8 ms to 14 ms) and Platter RotationSpeed (5400, 7200 and 10,000 rpm).

What are the Major brands in theMarket?

Quantum, Seagate, IBM, Fujitsu,Maxtor, Western Digital

What is FRU?Field Replaceable Unit. Device can be

replace in customer place. Hard Disk isconsidered a FRU.


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Importance of the Hard DiskImportance of the Hard Disk

How important is the Hard Disk to the PC? Performance: The speed at which the PC boots up and programs load is

directly related to hard disk speed. The hard disk's performance is alsocritical when multitasking is being used or when processing large amounts ofdata such as graphics work, editing sound and video, or working withdatabases.

Storage Capacity: A bigger hard disk can store more programs and data.

Software Support: Newer software needs more space and faster harddisks to load it efficiently.

Reliability: Hard disk is the most important component. Hardware can bereplaced, but data cannot. A good quality hard disk, combined with smartmaintenance and backup habits, can help ensure that the nightmare of dataloss doesn't become part of your life.


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Hard Disk Physical ComponentsHard Disk Physical Components

What are the major physicalcomponents in the Hard Disk?PlatterSpindle and spindle motorRead/Write HeadLogic Board

What is a Platter?Round, flat disks coated on both sideswith a special media material designedto store information.

What is the function of spindle and themotor?

The platters are mounted by cutting ahole in the center and stacking themonto a spindle. The platters rotate athigh speed, driven by a special spindlemotor connected to the spindle.

What is the Read/Write head use for?They are special electromagneticread/write devices used to eitherrecord information onto the disk orread information from it.

What is the function of the logicboard?Controls the activity of the othercomponents and communicates with therest of the PC.


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Storing the DataStoring the Data

How does the Hard Disk organized tostore information?

Storing data in tracks and sectors on thesurface ofplatter.

What is Tracks?

Tracks are concentriccircles, while

sectors are pie-shaped wedges ona trackA typical track is shown in yellow, while atypical sector is shown in blue.

What is a Sector?

Contains afixed numberofbytes - forexample, 512.

What is aCluster

Clusteris agroup ofsectors. The smalleststorage unit used to stored data.


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Types of IDE/ATA InterfaceTypes of IDE/ATA Interface

What is Hard Disk Interface?The interface between the computerand the hard disk drive.

Which are the 2 main categories ofInterface?

IDE and SCSI

What is IDE?

Integrated Device Electronics. Thedrive controller is integrated into theHard Disk Drive. Also known as ATA(Advanced Technology Attachment)

What is EIDE?Current implementation is EIDE orEnhanced Integrated DeviceElectronics. Also know as ATA-2.

What is the addition features of EIDE?

Supports hard disk greater than528MB. Supports for CD-ROM, Tapedrive, etc.


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Types of IDE/ATA InterfaceTypes of IDE/ATA Interface

Standard Speed Description

IDE/ATA 2.1 8.3 mb/s First ANSI standard.

Limited to 528MB and supports 2 devices

Supports PIO and DMA transfer mode.

ATA-2

Fast ATA

Up to 16 mb/s More than 528MB HDD.

Supports 4 IDE devices.Supports PIO and DMA transfer mode.

ATA-3 Little speedincrease

Improve version of ATA-2

Ultra ATA

Fast ATA-2

Ultra DMADMA/33

Up to 33.3 mb/s New DMA mode but supports slower PIO modes

Ultra ATA/66

Ultra DMA/66

Up to 66.6 mb/s Uses special 80-pin cable that providesadditional ground lines.

ATA-100 Up to 100 mb/s Technology for newer drive

Uses 80-pin cable

What are the types of IDE/ATA Interfaces?


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SCSI TechnologySCSI Technology

What does SCSI stands for?Small Computer Systems Interface

Why use SCSI instead of IDE?

An entirely different interface. It isnot a controller, like IDE, but aseparate I/O bus that is hooked to thesystem bus via a host adapter(expansion card).

How is SCSI devices supported in PC?

Inserts a SCSI card (HOST ADAPTER),into one of the expansion slots and

attaches SCSI devices to the cardusing the SCSI cable. Expansion slotcan be ISA or PCI

How many device can be connected?Up to 7 or 15 devices can be connected,depending on the type SCSI card.

How does each device being identified?

Each device is assigned an uniquenumber (LUN logical unit number).Either 0 to 7 or 0 to 15. The SCSIadapter normally takes 7 or 15.

What is the Priority?

Lower the ID, lower the Priority.

Does SCSI need devices need to beterminated?

Yes. The last device on each end theSCSI chain must be terminated usingterminating resistor.


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SCSI TechnologySCSI Technology

How is LUN

set?Using jumpers. Refer to picture below. What does the term LVD means inSCSI?

Low Voltage Differential. Standarddefining the use of uses 3.3 volt, whichconsumes less power, dissipates lessheat and is faster than HVD SCSI.


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SCSI StandardsSCSI Standards

What are the common SCSI standards?8-bit Narrow SCSI and 16-bit WideSCSI. See table below.

What are the type of Cable used?

50-pin for Narrow SCSI and 68-pin forWide SCSI.

What is IEEE 1394?Know as Firewire. It is Serial SCSI. Donot need termination and ID.

SCSI Interface Bus Transfer Rate

(MB/sec)

Max No ofDevices

No of Pins inConnector

SCSI-1 (Regular SCSI) Narrow 5 8 25

SCSI-2 (Fast SCSI)

Fast Wide SCSI

Narrow

Wide

10

20

8

16

50

68

SCSI-3 (Ultra SCSI)

Wide Ultra SCSI

Ultra2 SCSI

Wide Ultra2 SCSI

Ultra3 SCSI

Wide Ultra3 SCSI

Narrow

Wide

Narrow

Wide

Narrow

Wide

20

40

40

80

80

160

8

16

8

16

8

16

50

68

50

68

68

68


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SCSI ConnectorsSCSI Connectors


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Choosing Between SCSI and EIDE HDDChoosing Between SCSI and EIDE HDD

EIDE HDD SCSI HDD

Cost Cheaper Cost more

Performance Slower than SCSI Faster data transfer

Multi-tasking CPU can process data fromone device at a time

CPU can work with multipledevices connected toSCSI

No of devicessupported peradapter

2 devices per cable Up to 7 or 15 devices perhost adapter card

Multi-device workingconcurrently

NoOnly 1 device can work atone time. If HDD works,CD-ROM must wait.

YesMultiple device can worksimultaneously.

Good for large amount ofdata transfer.

What are the factors to consider in choosing SCSI or IDE HDD?


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Other Types of HDD InterfacesOther Types of HDD Interfaces

Interfaces Remarks

IEEE 1394

(Firewire)

Faster that EIDE and SCSI

Up to 400Mbp/sec

Supported by Windows 98 and Windows 2000

Slow to adopt by IndustryFiber Channel For high-end system that needs multiple hard disk.

Can connect up to 126 devices

Expansive

What are the other types of Interfaces available?


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Partition, MBRPartition, MBR

What is Partitioning a Hard Disk?Dividing it into logical volumes (C:, D: orE:). It first things to do when settingup a new hard disk, because partitionsare one of the major disk structuresthat define how the disk is laid out.

Does it involved the OS?No.

What is Master Boot Record?MBR or partition table is created duringpartition. It is the very first sector ofthe partition. It contains theinformation that describes logical disks.

What happen if MBR is damaged?

DOS may not even recognize that yourdisk exists. The partition sectorcontains a program which is executedevery time the PC is powered up. Thisprogram executes and reads the DOSboot sector or other operating system

boot sector.


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Formatting the Hard DiskFormatting the Hard Disk

What is Formatting?Creating of the OS Boot Sector, theFAT table and Root Directory.

Is the OS involved?

Yes.

What is the OS Boot Record?

Each drive has a boot sector whichcontains programs need to load theDOS system files.

What happen when the Boot Record isdamaged?

Damage to this sector can make yourdisk appear to be unreadable. Thissector is rewritten whenever you do a"SYS" or a "FORMAT /S" to a disk.

What is FAT (File Allocation Table)?It contains the location of each file andit indicates which location are free fornew file or file require more storagespaces.

Does each drive has a FAT?

Yes. Each drive has its own FAT. TheFAT system for older versions ofWindows 95 is called FAT16, and theone for new versions of Windows 95OSR2 and Windows 98 is called FAT32.

What is Root Directory?

Computer file system that is organizedas a hierarchy or tree. The rootdirectory is the directory that includesall other directories. (Unlike a realtree, a tree file system has only oneroot)


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File Allocation Table (FAT)File Allocation Table (FAT)

What is FAT16?A FAT directory holds information suchas name, file size, date & time stamp,the starting cluster number and the fileattributes like (archive, hidden, systemetc.).

When is FAT16 best use?On small 500mb drives because of thecluster size. It is about 2% faster thanFAT32. FAT performance drops offafter 400mb's on up.

What is the limit of FAT16?Supports up to 2 GB partition

What is VFAT (Virtual File AllocationTable)?A protected-mode version of the FATfile system, used by Windows 95. It iscompatible with the FAT system, themain difference being support for longfilenames

What is FAT32?Implemented from Windows 95 SR2onwards. It supports drives up to 2terabytes. FAT32 will not recognizeFAT

Why is FAT32 a better choice?It uses smaller clusters (e.g. 4kclusters up to 8 gigs). Up to 16GB,cluster size is 8KB; to 32GB, it's 16KB;and for partitions of 32GB and greater,the cluster size is 32KB


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Hard Disk Translation ModesHard Disk Translation Modes

What is Hard Disk Translation Modes?

Techniques used to overcome the HDD capacity limitation of 540MB. BIOScannot translate the structure of HDD beyond this capacity. CHS (cylinder,head, sector) mode is used for HDD below 540MB, and in actual there is notranslation at all. The BIOS view the hard disk according to the geometrypresented by the hard disk.

What are the Translation Mode Used?1. Extended CHS or Large mode

504MB to 8.4GB

Not popular

2. LBA (large block addressing)

More than 504MB

Automatically enable by BIOS

HDD as a list of addressable sectors, NOT CHS

Old HDD

NewHDD


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Data Transfer ModeData Transfer Mode

PIO

(Programmed I/O)

Old methods

CPU manages the transfer

5 modes:

PIO mode 0 to 4 (fastest)

DMA and Bus

Mastering DMA

DMA controller

CPU is not involvedNot popular

Ultra DMA HDD BIOS controls datatransfer

Highest transfer rates at

33, 44, 66 & 100 mb/s

Need HDD support

Need 80-pin IDE cable

Block mode Group multiple read or writecommands over the IDE/ATAinterface so that they can behandled on a single interrupt

Activated in BIOS

What the Data Transfer Mode used in HDD to speed up performance?


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Optimizing the Hard DiskOptimizing the Hard Disk

What are the tasks needed to maintain a Hard Disk?

1. Fragmentation

Using Disk Defragmenter to defragment the hard disk

Should not be running any other programs

Steps to perform Defragmentation

a) Start, Programb) Accessories, System Tools, Disk Defragmenter

2. Scandisk

Using Scandisk to repair cross-link and lost cluster

Steps to perform Defragmentation

a) Start, Programb) Accessories, System Tools, Scandisk


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Maintaining the Hard DiskMaintaining the Hard Disk

What are the 2 utilities provided byWindows to maintain the Hard Disk?

Disk Defragmenter

Scandisk

What is Disk Defragmenter?

Remove disk fragmentation. Should notbe running any other programs in thebackground, especially with Anti-virusor Screen Saver.

What are the steps to activate DiskDefragmenter?

a) Start, Programb) Accessories, System Tools, Disk

Defragmenter

What is Scandisk?

Scandisk is used to repair Cross-linkfiles, lost Cluster and update BadSectors.

What are the steps to activateScandisk?

a) Start, Programb) Accessories, System Tools,

Scandisk


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VcacheVcache

What is Vcache?What is Vcache?

It is a Disk Cache. It is used to keepalready read files in memory afterthey're no longer in use. If a file isneeded again it can be read from theVcache (ram) rather than from thehard drive. It replaces SMARTDRV disk

cache.

What is the Problem face with Vcache?What is the Problem face with Vcache?

By default, Vcache grows as large asBy default, Vcache grows as large aspossible. If your PC has 64 megabytespossible. If your PC has 64 megabytesof RAM, Vcache will quickly take up 30of RAM, Vcache will quickly take up 30to 40 megabytes of RAM. (The rest ofto 40 megabytes of RAM. (The rest ofthe memory probably will be claimed bythe memory probably will be claimed bysystem functions, your browser and sosystem functions, your browser and soon.). That means any other programson.). That means any other programscannot possibly runcannot possibly run

How to control Vcache?How to control Vcache?

Use Notepad to open the fullUse Notepad to open the fullSYSTEM.INI in Windows folder. LocateSYSTEM.INI in Windows folder. Locateand Change the Vcache section:and Change the Vcache section:

32 megs of ram:MinFileCache=2048/MaxFileCache=8192

64 megs of ram:MinFileCache=2048/MaxFileCache=16384

128 megs of ram or more:MinFileCache=2048/MaxFileCache=32768

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Chpt6 Storage - Hard Disk Drive