Introduction to Backup
Why backup is important
Just like your car, it's not "if" your hard disk fails, but "when."
A regular backup procedure is critical to make a duplicate copy of all the information stored
on your computer, which periodically should be stored off-site as well to
- disk failure
- virus infection
- corrupted database
- fire, tornado, flood, etc.
- theft of your computer
What type of backup device should be used?
Ideally your backup device should be large enough to
back up your entire system. Since most computers today have 10 gigabyte
plus hard drives, this pretty much limits you to tape and hard drive.
If you can find a reliable hard drive within your budget, it's by far the best
way to go for a daily backup.
The most popular backup devices are:
Removable hard drive
||Up to 80 gigabytes
||Hundreds, plus CD's
For more details on each of these, see
The most common backup media for PC's is large-volume tapes. Due to
decreasing costs, removable hard disks are becoming increasingly popular.
How often should backup
There can sometimes be a delay between the time data is corrupted (damaged) and the time the damage is discovered. Because of this,
if you're using a database that's critical to your business, it's important to use more than one backup tape so you can go back a day, several days, or even several weeks to be sure you can get to a completely undamaged version.
Since tapes are much less expensive than hard disks, generally they're used for
this procedure since 12 different tapes - minimum - are required.
most frequently-used rotation scheme is Grandfather -
Father - Son, which uses the following:
1 through Month 3
1 through Week 5
Monday through Thursday
appropriate Daily tape
appropriate Weekly tape
business day of the month
appropriate Monthly tape
As important as doing a backup is testing it to make sure that you can copy from the backup medium onto your computer (called a "restore"). If you haven't
actually done a restore, you don't have a reliable backup.
**Types of Backup
Full backs up everything;
Differential backs up only the files changed since the last full
Incremental backs up only the files that have changed since the last
Full or Differential backup.