| What does it do?
Your hard disks store information documents, applications, the Mac OS, and more. Unlike memory (RAM), which is a temporary working store, the contents of your hard disk remain intact when your Mac is shut down and disconnected from the mains. However, although convenient for both reading and writing information, hard disks aren’t as permanent storage as ‘archival’ media, such as recordable CDs. How does it work?
Hard disks are sealed units which must never be opened. Inside are one or more metal platters coated with magnetic particles, and spun at high speeds. Data is recorded by aligning the particles using special sensor heads which move just above the platter surface. The sensors also read from recorded data. Hard disks need a firmware and hardware interface to talk to your Mac: popular schemes include the older SCSI, widely used ATA or IDE, and newest USB and FireWire. These require special electronics, normally fitted outside the hard disk. What can go wrong with it?
Crashes are the most common serious problem, in which some of the contents of the disk become corrupted. This may just take out a single document, or could occur in a special part of the disk containing critical control information the latter can trash the contents of the entire disk. Errors may now be very infrequent, but they do occur at random and in crashes, so all important items on a hard disk must be backed up to more permanent storage. Individual files may be stored in separate blocks scattered across the disk, where there’s free space; although not an error as such, if too many files are fragmented in this way, access to them may slow, and Mac OS 9 may even become unstable. How can I upgrade it?
Being sealed units, you can replace a slow, small disk with a larger, faster one, or add more using one of the connection interfaces, either internally or externally. Tower systems usually have free space to add disks inside, but they should be mounted properly on plastic ‘sledges’ available to dealers. External disks can be moved to other machines, but are usually more expensive. Further info
Web sites with further information include: Ask Al, Alsoft’s disk problem solver, at www.alsoft.com/AskAl/index.htm; DriveSavers recovery tips for crashed disks, and so on, at www.drivesavers.com/5/index.html; and Blue Planet’s Tech Page, with jumper and tech info for virtually every hard disk ever made, at www.thetechpage.com/cgi-bin/default.cgi. | |
