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How a Hard Disk Drive Works
Hard Disk Assembly

Last updated: 2/5/2002

The purpose of this article is to provide just the right balance of technical detail to convey a good insight into the innards of a hard disk drive and how if basically works without burdening the reader with excessive technical detail.

Hard Disk InardsHARD DISK ASSEMBLY.  A hard disk drive consists of a motor, spindle, platters, read/write heads, actuator, frame, air filter, and electronics.  The frame mounts the mechanical parts of the drive and is sealed with a cover.  The sealed part of the drive is known as the Hard Disk Assembly or HDA.  The drive electronics usually consists of one or more printed circuit boards mounted on the bottom of the HDA. 

A head and platter can be visualized as being similar to a record and playback head on an old phonograph, except the data structure of a hard disk is arranged into concentric circles instead of in a spiral as it on a phonograph record (and CD-ROM).  A hard disk has one or more platters and each platter usually has a head on each of its sides.  The platters in modern drives are made from glass or ceramic to avoid the unfavorable thermal characteristics of the aluminum platters found in older drives.  A layer of magnetic material is deposited/sputtered on the surface of the platters and those in most of the drives I've dissected have shiny, chrome-like surfaces.  The platters are mounted on the spindle which is turned by the drive motor.  Most current IDE hard disk drives spin at 5,400, 7,200, or 10,000 RPM and 15,000 RPM drives are emerging.

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Copyright, Disclaimer, and Trademark Information Copyright © 1996-2006 Larry F. Byard.  All rights reserved. This material or parts thereof may not be copied, published, put on the Internet, rewritten, or redistributed without explicit, written permission from the author.