Hard disk drives in constant danger


February 03, 1992|By PETER H. LEWIS

A hard disk drive is never more than one second away from disaster. A power fluctuation, a computer virus, a faulty circuit, a corrupted file, a hard knock on the desk, a burglar, an infestation of gremlins -- any one of them can render your hard disk as useless as a stone, sending data into oblivion.

Luckily, you have a current backup. You DO have a backup, don't you?


Backing up a hard disk is the process of copying all or some of its files onto another disk or tape. It does not help to copy files from one part of the hard disk to another part of the same hard disk.

If the hard disk fails, as it will, a backup allows the user to reverse the process.

All the file copies can be restored to the hard disk after it is repaired or replaced. The only losses are the files created since the backup was made.

Sometimes the hard disk fails mechanically. More often, it continues to work but the all-important file-allocation table or boot sector of the disk goes bad, creating the computer equivalent of amnesia.

The computer issues a message along the lines of "Sorry, I don't have a hard drive," or, "Too bad, the file you worked on yesterday isn't here any more."

There is often no comfort in having a service technician nearby.

Be forewarned: especially for warranty work, many technicians hTC will simply replace or reformat a hard disk rather than go to the trouble of trying to fix it. In other words, they will sacrifice your data for their convenience. Sometimes they have no choice.

Backups are insurance policies for your data. With luck, you will never need them.

How often should backups be made? It depends on how much time and effort you are willing to spend. Are you willing to %J sacrifice a week's worth of work to avoid making a backup each day?

Some people are comfortable with monthly backups. Some companies perform backups twice a day. Some do it constantly through a process called disk mirroring, using two hard disks at once.

The most common backup mediums are a 5.25-inch floppy disk or a 3.5-inch diskette, which unlike the hard disk can be removed from the machine and stored in a safe place.

A safe place is not necessarily next to the computer. Burglars often grab boxes of diskettes along with the computer, and a fire or flood that destroys a computer will not spare diskettes.

For greatest security, make three backup sets and keep one "off site."


True paranoiacs will make three sets at the same time. A

more practical alternative is to make a three-generational backup, copying over the oldest set on a rotating basis.

As an example using daily backups, on Thursday, Monday's set of disks is overwritten. On Friday, Tuesday's set is overwritten, and so on. If the new Friday set is defective or lost, at least you still have Thursday's set.

The diskette drives that come in newer computers can store 1.2 megabytes (millions of characters) or 1.44 megabytes on a single diskette, depending on the type of drive.

It takes at least a couple of boxes of diskettes, at 10 to a box, to hold the contents of standard 40-megabyte hard disks.

(The numbers of megabytes will not match because most backup programs use some form of data compression. Compressed files are "exploded" when they are copied back onto the hard disk.)

It is possible to copy all the files onto diskettes using the basic DOS COPY command, but that is like digging a ditch with a teaspoon. The latest version of DOS comes with an improved backup program that automates the process to some degree.

However, it makes sense to invest in a specialized backup program.

The most popular are Fastback, Norton Backup or PC Tools. On the Macintosh, popular backup programs include Fastback and Retrospect.

It takes at most half an hour to become adept at using a backup program, and depending on the amount of data, perhaps another half hour to make a full set of backup diskettes.

After that, the user may find it makes sense to back up only the files that have been changed since the complete backup was made. These so-called incremental backups can take a minute or less, making them pretty cheap insurance.

We keep a formated diskette in the computer's A drive at all times and use it for impromptu backups, one file at a time, depending on what we are working on. Before storing a file on the hard disk, we also store it on a diskette. The annoyance of storing the same file twice is outweighed by the sense of security.

But as hard disk capacities grow to 80, 100 or even 200 megabytes in standard desktop computers, backing up to diskettes becomes cumbersome even with data compression.

Next week we will discuss alternatives like tape cartridges, external drives, disk mirroring and removable drives.

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