HARD DISK DRIVE

A non volatile storage device

Basic parts of hard disk

Platters Actuator Arm Read & Write head (slider) Spindle motor Voice coil Actuator Power connector Jumper pins

Sectors & Tracks Data is stored on the

surface of a platter in sectors and tracks. Tracks are concentric circles, and sectors are pie-shaped wedges on a track.A typical track is shown in yellow; a typical sector is shown in blue. A sector contains a fixed number of bytes -- for example, 256 or 512

Technology lies behind Data storageHDDs record data by magnetizing ferromagnetic material directionally, to represent either a 0 or a 1 binary digit. They read the data back by detecting the magnetization of the material.

A cross section of the magnetic surface in action. In this case the binary data is encoded using frequency modulation

Platters . A typical HDD consists of a

spindle that holds one or more flat circular disks called platters, onto which the data is recorded. The platters are made from a non-magnetic material, usually aluminum alloy or glass, and are coated with a thin layer of magnetic material, typically 10-20 nm in thickness with an outer layer of carbon for protection. Older disks used iron(III) oxide as the magnetic material, but current disks use a cobalt-based alloy

Actuator Arm - This holds the read/write heads and is

controlled by the mechanism of actuator. The arm is able to move the heads from the hub to the edge of the drive. The arm and its movement mechanism are extremely light and fast. The arm on a typical hard-disk drive can move from hub to edge and back up to 50 times per second.

Voice coil Actuator

Read &Write head

read-and-write heads that operate very close (tens of nanometers in new drives) over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it. There is one head for each magnetic platter surface on the spindle, mounted on a common arm.

About material of R&W Head

The read element is typically magneto-resistive while the write element is typically thin-film inductive

Landing Zone & load/unload

“A landing zone is an area of the platter usually near its inner diameter (ID), where no data is stored. Modern HDDs prevent power interruptions or other malfunctions from landing its heads in the data zone by parking the heads either in a landing zone or by unloading (i.e., load/unload) the heads. Some early PC HDDs did not park the heads and they could land on data.

Hard Disk Drive with Platter & motor removed