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HARD DISK DRIVE AND CONTROLLERS

INTRODUCTION: -

Hard disk drives are similar to the floppy disk drives with some major differences. Firstthe disk rotates approximately 20 times faster than the floppy disk at a speed of 7200 to10,000 rpm as opposed to 360 revelations per seconds the read and writes head isflying one.

BASIC STRUCTURE OF HARD DISK DRIVE: -

The hard disk drive is a sealed unit that holds most of the data in a computer system. Ahard disk drive is made up of many components, and many are various types suds asst506 interface, ESDI (Enhanced Small Device Interface), IDE (Integrated DeviceElectronics), SCSI (Small Computer System Interface) etc., in these entire however, thebasic mechanical components are generally the same they are:

1. Disk platters2. Read and Write heads3. Head Actuator (Stepper or Voice coil)4. Spindle Motor5. Logic Board6. Connectors etc.

The platters spindle motor; heads and head actuator mechanism are usually containedin a sealed champers called hard disk assembly (HDA). The HDA generally formssingle assembles, since if can be opened in a dust free, environment only.

PLATTERS: -

The typical hard disk has one or more platters or disks of generally 5.25" or3.5" diameter. Cold high capacity drives used 8" and 14" platters also. All theseplatters are mounted on a single shaft, and driven (at about 7,200rpm to 10,000 rpm) bythe spindle motor. The platters are about 0.05" thick and coated with a magnetically(aluminum) retentive substance or media, which is actually responsible for the storingthe data. The thickness of this media is about 30 microns.

READ AND WRITE HEAD: -

The hard disk drives have read and write head for each platters surface. Depending

upon the derive model number, there may be 4 to 15 heads, all which are mounted oncommon movement mechanical each head is mounted on an arm that is spring loadedto force the heads on to the platters. At rest, the heads are in contact with the platter.But, when the drive is spinning out full speed, air pressure, it formed below the read and

write head, which lifts it away from the platters.

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SPINDLE MOTOR ASSEMBLY: -

Together the platters rotate as a unit on a shaft, called the spindle. Typically the short

connects directly to a spindle motor that spins the entire assembly. Most hard disksuse servo-controlled spindle motors, which constantly monitor their own speed usingoptical or magnetic sensors and automatically compensate for any variation. Typicallyhard disk platters spin at about 7200rpm to 10,000 rpm.

CONTROLLED ELECTRONICS BOARD: -

All the electronics in the disk drives is located on the logical boards. This electronicscontrols the spindle motor, head actuator, read and write head signals from or to thehead, the signal interface between the hard disk controller and drive etc.

HARD DISK STRUCTURE: -

Platters of the hard disk are made from an aluminum alloy. The aluminum serves assubstance to which a magnetic medium is affixed either with a binder or mechanically.In addition to that it in coated writer oxide, by the method of electroplating.

SENSORS: -

Concentric circles on a disk that are numbered from the outside starting of 0 to mostfloppy disk have either 40 or 80 tracks per side, which hard disk have many more someas many as 1000.

SECTORS: -

A sector is that part of a track lying with in what could be farmed a "pick slice" of thedisk.

CYLINDERS: -

1Tracks of the same dos number on each platter form a cylinder. Cylinder made ofsame tracks on different platters.

CLUSTERS: -

A clusters is a set of configures sectors, which a hard disk may have four or moresectors per clusters.