Information Technology Reference
In-Depth Information
Although incremental backups can be relatively fast and take up
relatively little space, file recovery involves updating based on the
last full backup, an interaction that involves processing. Many relia
bility guidelines therefore suggest that you check this process regu
larly; that is, on a periodic basis it is important to take an old full
backup, apply changes, and check that the system really can be re
stored correctly. Backups can provide a valuable measure of relia
bility, but only if they work properly.
As an additional precaution, if something does go wrong, you
should be careful in how you use your backups. For example, if a
disk drive malfunctions, ruining the copy of a file on one disk, then
inserting the backup copy into the same disk drive might well ruin
the backup copy as well. At the very least, care is needed to deter
mine the cause of the problem first, to be sure the same problem
does not occur again.
Your computer files and information, therefore, can be rela
tively secure when they are under your care and you back them up
as necessary. You have a good chance that they'll be there when you
want them. It becomes more of an issue when you trust your files to
someone else or to a resource beyond your control. Take, for in
stance, your money; you likely use ATMs all the time, entrusting a
computer networking system with your hardearned cash. How can
you be sure that the machines running your transactions are com
pleting them as instructed? What would happen if the ATM
crashed? Let's take a look at ATMs and explore this further.
As you might expect, maintaining bank records requires consid
erable care, and special procedures are established to anticipate the
various circumstances that might arise related to computer crashes
and malfunctions. Let's consider three situations that might arise
when you try to transfer money from your savings account to your
checking account:
1.
A crash or malfunction occurs before you try to make your
transfer.
2.
A crash or malfunction occurs after you have made your transfer.
