Taking care of hard disks
Keep away from dust and high temperatures. Make sure the fan is working.
Never move the drive while its on. Scooting it across the desk surface is worse than picking it up.
Turning hard disks on and off
You should always turn on your hard disks - and any other peripherals - first, wait until the hard disk is up to speed, and then turn on your Mac. For shutting down follow exactly the opposite procedure.
If you accidentally shut off a hard drive - don't panic. Just turn it back on. If it doesn't work,
get hold of me.
Organizing a hard disk
a place for everything and everything in its place
a fleet is only as fast........
If you have more than one Hard Drive connected to your computer, returning to the desktop from an application will only be as fast as the slowest drive.
Initializing Disks
All disks, hard or floppy, have to be intialized (or formatted ) before you can use them. In many case they come pre-formatted for the Macintosh. Imagine the disk like a huge, round, blank sheet of paper. What formatting does is draw a numbered grid, like graph paper, that gives you boxes to put information in. Imagine information as filling in one of these little boxes or leaving it blank. The finer you make the grid, the more little squares there are to put information in, so high density disks can contain more information in the same space.
The grid itself occupies some space, so you have less room on a formatted disk than on an un--formatted one
The directory and desktop files
Initializing reserves part of a disk for special files, one of which is called the directory. Like the directory in an office building, which tells you which companies are in which offices, the directory on a disk keeps track of which files are in which sectors. Every time you save a file to a disk its location is saved in the directory.
Initializing also reserves disk space for the desktop files. They store the size and location of open windows, how the contents of the windows are viewed (by Icon, Name or whatever), what each applications icons look like, the Get Info information for every file, etc. In other words, the directory keeps track of where files are stored on the disk and the desktop files keep track of how their icons and windows are displayed on the screen.
Deleting and recovering files
What happens when you delete a file? In information isn't actually removed, the directory is simply told that the sectors previously occupied by that file are now available for storing new files. The deleted file remains on the disk, until its overwritten by new information being put into the sectors in which it's stored. So unless the information has been overwritten, the deleted files are recoverable. There are utilities available to recover files (e.g., Norton Utilities, MacTools, etc.).
Rebuilding the desktop
The more windows and different kind of icons you have, and the more often you have moved things around, the larger the desktop files get; periodically you need to rebuild them ,which tidies them up by getting rid of obsolete information. Sometimes, the desktop files become so big that starting up and returning to finder from an application can become pretty sluggish. That when you should rebuild your desktop. To rebuild the desktop on the startup disk, hold down
Option + Command (Apple)
keys while starting your Mac.
Disk Fragmentation
Each sector on a Macintosh floppy holds 512K (or half a K) of information. On hard disks, sectors can be as large as 4K ---- and they are getting bigger as hard disk sizes increase. Still, most files are bigger than 4K, thus they occupy several sectors. Large files may even take up several tracks.
When a disk is relatively empty, a file is stored on it in contiguous sectors, one after the other; this makes for fast saves, and fast reads when you want to open the file later. But after you have been using your disk for a while, things can get messy. When files are not stored away in contiguous sectors on the disk, the disk is fragmented (its actually the files that are fragmented). If this happens you need to fragment it by using some de fragmentation tools, such as Norton's Speed Disk. Make sure you backup up the disk before you do this.
The notes are based on The Macintosh Bible, 4th Edition, Arthur Naiman et. al., Peachpit Press, 1987-92.
| Return to Molecular Microbiology Home Page
Send suggestions and comments to: www@borcim.wustl.edu |
WWW
Department of Molecular Microbiology, Box 8230
Washington University School of Medicine
St. Louis, MO 63110-1093 USA |
Tel 314-362-7059
FAX 314-362-1232
Last updated September 7, 1995. |