Hard Disk Drive Components Basic components of a typical hard disk drives

are: Disk Platters Read/ Write Heads Head Actuator mechanism Spindle motor Logic Board Cables and Connectors Configuration items (like jumpers, switches etc)

Typical hard disk drive components

Hard Disk Platters(Disks)Have one or more platters or disks3 ½” are the most popular foe desktop

computers2 ½” and smaller are for notebooks and portable

devicesNo. of platters is limited by its vertical physical

sizeMaximum no. seen in 3 ½” drive is 12But most have 6 or fewer

Originally made from aluminium/magnesium alloy

Latter platters made of glass were madeOne such made by Dow corning corp.

Called MemcorComposed of glass with ceramic implants,

enabling it to resist crackingOffers great rigidity than metalsThermally stable than aluminium platters i.e(do not expand with changes in temperature )

• All modern drives use glass or glass-ceramic platters

Fig: An example of a platter

Platters

Recording MediaAll platters are covered with

magnetically retentive substance called medium

Three popular magnetic medium are:Oxide mediaThin-film mediaAFC(anti-ferromagnetically coupled)

media

Oxide MediaMade up of various components, iron

oxide as main Oxide coated platters are brownish or

amberSince oxide medium are soft, it subjects

to head crash damageCurrently very few drives use oxide

media

Thin-film MediaIt is thinner, harder and more perfect than

oxide mediumAlso known as plated or sputtered mediaPlatted media are created by depositing

magnetic medium Sputtered media are created by

1. Coating platters with layer of nickel phosphorus

2. Applying cobalt alloy in complete vacuum deposition process

AFC MediaCalled anti ferromagnetically

coupled mediaIt consist of two magnetic layer

separated by a thin 3-atom layer of element ruthenium

IBM uses term “pixie dust” to refer this layer

This AFC coupling causes the entire thickness to be the difference of top & bottom layer

IBM introduced AFC with 2 ½” Travelstar 30GN series notebook in 2001

In desktop 3 ½” drives started with Deskstar 120GXP

Now used by Hitachi Global Storage Technologies

AFC coated media looks like a mirror

Read / Write HeadsEach platter ha two sets of read/write

heads

Set of read/write heads

When drive is at rest, heads are forced into direct contact with platters

When spinning, air pressure develops below the head, lifts them off

Distance b/w head & platter while spinning can be b/w 0.5 µ-in. to 5 µ-in