Backups Keep Your Computer out of Jeopardy
This article describes a simple backup strategy
to protect your valuable computer data.
There are no good reasons for not doing regular backups. Nothing
should be allowed to interfere with them.
© Copyright 1995-2003 Mitchell G Theophila.
All Rights Reserved.
This is not a game
User 1: "We just had the power go out while I was using my computer. Now, every
program screen we bring up has garbage all over. What can we do?"
User 2: " I accidentally wiped out my boss’s entire calendar from every PC on
the network. What can I do? "
User 3: " All the machines in our office caught a computer virus from the game
we've been passing around. We can't run any of our business programs any more. What can we
do?"
If I knew nothing more about their situations, I would tell each user "Go to your
backups and restore your files." For users 1 and 2, this would be the most recent
backup; user 3 would use an older one made before the infection.
Without backups, there is no easy recovery even to minor data losses. Typically, the
user must reinstall programs or re-enter data from scratch. This is error-prone. Some data
or functions may never be fully recovered. Businesses have failed because data lost from
their computer files could not be restored completely or correctly after a catastrophe.
Not making backups is like going to sea without a life jacket, or riding a unicycle on
the potholed berm of a busy street. It's like betting everything in Final Jeopardy when
you're sure to win anyway. In more direct language, NOT MAKING BACKUPS IS DANGEROUS AND
STUPID.
Defining the Terms
backup (noun) 1. A copy of a file, preferably on a physical volume different from
the original. If something happens to the original file or volume, the file can be
"restored" from its backup copy. Example: "Having a backup of a file
means that no matter what happens to the original file, it can be restored." 2. The
procedure of making a backup. Example: "Do your backups."
backup (verb) To make a backup; usually, to copy data from hard disk onto a tape or
floppy disk. Example: "It's possible to backup just one file, but to save effort
you'll probably backup several files at once." The reverse operation is restore.
Backups establish a safety net
Because files change, you must repeat the backup procedure over time. A daily backup
provides a daily safety net; a file-destroying disaster will never lose more than one
day's work. In some businesses, the volume of work mandates a backup several times a day.
When files are changing quickly, backups go "stale" (out of date) fast. Like
produce at the market, backups are usually best when "fresh". But there are two
important exceptions.
1. Sometimes files change for the worse. A "bad" change to a file might
be a virus infection or an improper close of an accounting month. After a "bad"
change, a backup of that file only protects something you don't want anyway.
You may unfortunately not find out that files have gone bad until after they've been
backed up. In these cases you'll not want to restore from any such backups.
2. The backup process itself can fail for any number of reasons. The tape or floppy
drive might break, or your office power might suddenly fail, during the backup itself.
If you're lucky, you'll discover the problem when it occurs. If you aren't, you'll
think you have a good backup when you don't have one at all... and then suddenly need it!
Backup retention
These special cases are the times when having an older backup is important. So how long
do you keep a backup?
If you are backing up to a resuable medium, like tape or disk, you have to decide
whether to overwrite your backups. In the past most most shops eventually did,
because it was too costly to use a backup tape or disk only once. A tape would be
reused, and the old backup data on it lost, after it reached a certain age.
Nowadays, many shops back up to writable CD; it is not reusable but CD's are very
inexpensive. The backups can be kept indefinitely.
Backup generations for reusable media
If you are reusing your backup medium, you should keep several sets or generations of
backups. Backups can be arranged from oldest to "youngest"; staying with the
family-oriented theme, we call the second-newest backup the "parent" and the
third-newest the "grand-parent". It’s best to keep at least three
generations of backups. In your particular business, you may have reasons to retain data
for a longer period of time.
Have at least two backup generations; never rely on only one. If you always back up
to the same disk or tape volume, overwriting your last backup, it’s only a little
better than not doing any backups at all. If a file ever changes for the worse, but you
don't catch it before it gets copied to your (only) backup volume, you've not only lost
your good original file; you’ve also lost your backup. Or if something goes wrong
during the backup, your one good backup could be overwritten by a bad one and you may not
even know until you need to do a restore. A third generation gives you an extra backup in
case two generations are overwritten before you learn about and correct the problem.
More about backups
Most backup software can tell whether a file has been changed since the last time it
was backed up, making possible another option for the user: a backup of changed files
only. This bypasses routine backups on files that never change--eliminating a lot of
needless backing up--but it also requires a little more backup management. It also
complicates restore operations: if a given file wasn't changed prior to a particular
backup, then you won't find that file on that backup. You may have to spend some time
searching for the backup volume that has the specific file that you want to restore.
Here is a generic backup plan for reusable media which is a good sample strategy for
situations without extra requirements: Make a weekly backup of everything (a
"full" backup). Then, make daily backups of only changed files until it's time
for next week's "full" backup. Each daily backup should be made to its own
diskettes or tape volumes, so the first days' backups are not overwritten by later ones.
The weekly full backup and all its successive daily changed-only backups form a backup
generation. Next week, start the next generation with another set of backup media. If you
use a grandparent/parent/child scheme, overwrite the "grandparent" backup when
you make a new "child".
For even more safety, keep some of your backups in a secure location off-site. If your
office contents are ever destroyed, you can recover computer operations whose backups are
safe someplace else. For offsite storage in the "grandparent/parent/child"
scheme, select a generation and designate it as the offsite backup. This means your weekly
backup procedure will include a round trip to the offsite location to exchange the old
off-site backup with this week's version. If you are using the "parent" for
offsite storage, the off-site "parent" becomes the "grandparent" and
should be brought back; the old "child", now the
"parent", takes its place.
© Copyright 1995-2003 Mitchell G Theophila.
All Rights Reserved.
All registered trademarks shown are the property of their owners.
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