storage devices - hdd

8/6/2019 Storage Devices - HDD

1/25

Storage Devices - HDD

Computer Hardware and Software

Technology


2/25

M agnetic Storage

P ermanent or semi-permanent computer datastorage works by either optical or magneticprinciples or, in some cases, a combination of the two.In the case of magnetic storage, a stream of binary computer data bits (0s and 1s) is

stored by magnetizing tiny pieces of metalembedded on the surface of a disk or tape ina pattern that represents the data.


3/25

History of magnetic storage

J une 1949they were working on was the first magneticstorage device for computers, and itrevolutionized the industry.

May 21, 1952IBM announced the IBM 726 Tape Unit with the

IBM701 Defense Calculator, marking thetransition from punched-card calculators toelectronic computers.


4/25

History of magnetic storage (cont)

September 13, 1956first computer disk storage system as part of the305 RAMAC (Random Access Method of

Accounting and Control) computer.


5/25

Define: Hard Disk Drive

is a sealed unit that a P C uses for nonvolatiledata storage. Nonvolatile, or semipermanent,storage means that the storage deviceretains the data even when no power issupplied to the computer.contains rigid, disk-shaped platters, usually

constructed of aluminum or glass.


6/25

HDD - Inside


7/25

HDD Form Factor


8/25


9/25

HDD - Operation

HDD consists of these ff:

TracksSector P latters


10/25


11/25


12/25

C aution

It is strongly recommended that you do noteven attempt to open a hard disk drive's HDAunless you have the equipment and expertiseto make repairs inside. Most manufacturersdeliberately make the HDA difficult to open todiscourage the intrepid do-it-yourselfer.

Opening the HDA voids the drive's warranty.


13/25

Disk Formatting

Two formatting procedures are requiredbefore you can write user data to a disk:

P hysical, or low-level formattingLogical, or high-level formatting


14/25


15/25


16/25

Disk Formatting Partitioning (cont)

FAT32 (file allocation table, 32-bit) An optional file system supported by Windows 95 OSR2(OEM Service Release 2), Windows 98, Windows Me,and Windows 2000/X P .

NTFS (Windows NT File System)The native file system for Windows NT/2000/X P thatsupports filenames up to 256 characters long andpartitions up to (a theoretical) 16 exabytes. NTFS alsoprovides extended attributes and file system securityfeatures that do not exist in the FAT file system.


17/25

C aution

FDISK, DISK P ART, Disk Management, and other disk partitioning tools included in operating systemscan't be used to change the size of a partition; all

they can do is remove or create partitions. The actof removing or creating a partition destroys andloses access to data that was contained in thepartition or that was on that part of the disk. To

manipulate partitions without destroying data, youcan use third-party utility programs, such as P artitionMagic from Symantec or P artition Commander fromV-Communications.


18/25

B asic Hard Disk Drive C omponents

Disk plattersRead/write headsHead actuator mechanismSpindle motor (inside platter hub)Logic board (controller or P rinted CircuitBoard)

Cables and connectorsConfiguration items (such as jumpers or switches)


19/25

B asic Hard Disk Drive C omponents

(cont)


20/25

R ead/Write Heads


21/25

C aution

The small size of the gap between theplatters and the heads is why you shouldnever open the disk drive's HDA except in a

clean-room environment. Any particle of dustor dirt that gets into this mechanism couldcause the heads to read improperly or possibly even to strike the platters while the

drive is running at full speed. The latter eventcould scratch the platter or the head, causingpermanent damage.


22/25

Head Actuator M echanisms

Stepper motor actuatorsVoice coil actuators


23/25

Stepper M otor Actuators

A stepper motor is an electrical motor thatcan "step," or move from position to position,with mechanical detents or click-stoppositions.Stepper motor mechanisms are affected by avariety of problems, but the greatest problem

is temperature.


24/25

Stepper M otor Actuators (cont)


25/25

Hard Disk Features

CapacityP erformance

Transfer rate Average access time

ReliabilityCost

storage devices - hdd

Documents