Magnetic Storage - Hard disks

Vincent Bockaert,

The building blocks of digital images are "bits", which can either be "zero" or "one". Magnetic storage devices such as hard disks distinguish a "one" from a "zero" by changing the magnetic properties of the disk in that location. The great thing about hard disks is that their capacities are constantly increasing while prices are constantly dropping. Two hundred gigabyte[1] hard disks (3.5" IDE 7200rpm with 8 MB cache) currently retail under US$100. Such hard disks can hold about 70,000 six megapixel JPEG or 23,000 six megapixel uncompressed RAW images. That's about 700 JPEG or 230 RAW images per dollar.

Portable housings exist with built-in international 100-240V power supply, USB 2.0 (Hi-speed), and FireWire IEEE1394 connections, costing between US$50 to US$100. To avoid overheating, get a case with a large diameter cooling fan below the hard disk. Note that the market is gradually moving towards SATA (Serial ATA) drives and away from the older and slower IDE drives. However, the choice of external housings for SATA drives is still limited.

If you store images on your computer, it is recommended to store them on a dedicated partition (or if you have multiple hard disks, then ideally on a different physical drive) than your operating system (e.g. use C:\ for the operating system and software, and D:\ or E:\ for your images). This ensures that if your operating system crashes and you need to reinstall it, your images will be preserved.

Technical Footnote

  1. (1) Usually "200" stands for 200 billion bytes, which is equivalent to 186 gigabytes.
This article is written by Vincent Bockaert,
author of The 123 of digital imaging Interactive Learning Suite
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