Backup's

Backup's

Data backups are a form of preventive maintenance. They ensure that, should a problem develop with

your PC or system that jeopardizes your data, you have a copy of the data to restore when the problem is solved. On top of that, they just make good sense. There are any number of threats to the integrity of your data, hardware failures, beta-test software, operator error, and viruses. It may seem a bit paranoid, but just because I'm paranoid doesn't mean they aren't really trying to get me.

Creating a data backup 

Tape is a good medium to use for creating a backup of hard disk data. Making a backup of files is a safety precaution taken to ensure that data outlives the device on which it's stored. A cardinal rule of computing: Back up files regularly, and then back up the backups.

Most operating systems include utilities for creating a backup (see Part V ) and backup software is

usually included with tape, recordable CD, and other writable media drives. Of course, a variety of

software packages specifically designed to perform backups are available for purchase.

Backup software offers some advantages over just copying a file to a removable medium. Most offer

data-compression techniques to reduce the number of disks or tapes needed to hold the archived data.

Many also offer cataloging routines and single directory or file-restore capabilities.

You can create four different types of backups:

l Archival backup (or full backup): Contains every file, program, table, and so on from the hard

disk.

l Incremental backup: Contains only the files that have been modified since the previous backup.

l Differential backup: Copies all the data added or modified since the last full backup.

l Copy backup: Created by using a copy command to write a duplicate of a file, directory, or disk

to another media.

It's wise to rotate a series of tapes or other media relative to the number of increments to be regularly

captured. For example, if daily backups are made, you should use seven sets (or possibly only five, if the office works only five days a week) of backup media. It's also good practice to make an archival backup at least once per cycle with two or more incremental backups filling out the cycle. For example, you can create an archival backup once a week and create a daily incremental backup during the rest of the week.

Whatever cycle you use, the backup should be a comfortable safety net for the system that matches how frequently, and how much of the data is affected by changes.

Storing data on tape 

Back in the dark ages of personal computing, back even before floppy or hard disks, the only permanent storage media available was cassette tapes--the same ones used for music. Before then, except for some very early use of punched paper tape, you just didn't store data between runs of the PC. Each time you wanted to run your BASIC program, you had to re-enter it and the data. Regardless of how you feel about tape today, at one time, it was a godsend.

Tape is a somewhat unique medium in comparison to the other writable permanent data storage media

available to PC users today. Whereas most of the other media are direct access, tape is a serial, or physically sequential, access media. If you want to hear the third song on a music cassette, you must

first fast forward over the first two songs. The same holds true for accessing the third record of a tape

file.

Tip

Tape is primarily a backup media today, and many larger systems, especially network servers, have either an internal or external tape drive. This is a good use of the media, its serial nature, and its relative compact size. Some problems exist with using tape, but they're avoidable with proper care and diligence.

You should rotate tapes regularly, store them in a cool, dry place (look for this tidbit on the test), and

replace them at least once a year.

If intermittent problems begin showing up in a rotated group of tapes that are used for daily backups, the problem could be the age of the tapes or perhaps the tape heads need cleaning.