Backups; Different Data: Different Backup Needs - Red Hat ENTERPRISE LINUX 4 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual

Chapter 8. Planning for Disaster

8.2. Backups

Backups have two major purposes:
To permit restoration of individual files
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To permit wholesale restoration of entire file systems
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The first purpose is the basis for the typical file restoration request: a user accidentally deletes a file
and asks that it be restored from the latest backup. The exact circumstances may vary somewhat, but
this is the most common day-to-day use for backups.
The second situation is a system administrator's worst nightmare: for whatever reason, the system
administrator is staring at hardware that used to be a productive part of the data center. Now, it is little
more than a lifeless chunk of steel and silicon. The thing that is missing is all the software and data
you and your users have assembled over the years. Supposedly everything has been backed up. The
question is: has it?
And if it has, can you restore it?

8.2.1. Different Data: Different Backup Needs

Look at the kinds of data
data hardly ever changes, and some of the data is constantly changing.
The pace at which data changes is crucial to the design of a backup procedure. There are two reasons
for this:
A backup is nothing more than a snapshot of the data being backed up. It is a reflection of that data
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at a particular moment in time.
Data that changes infrequently can be backed up infrequently, while data that changes often must
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be backed up more frequently.
System administrators that have a good understanding of their systems, users, and applications should
be able to quickly group the data on their systems into different categories. However, here are some
examples to get you started:
Operating System
This data normally only changes during upgrades, the installation of bug fixes, and any site-
specific modifications.
Tip
Should you even bother with operating system backups? This is a question that many system
administrators have pondered over the years. On the one hand, if the installation process is
relatively easy, and if the application of bugfixes and customizations are well documented and
easily reproducible, reinstalling the operating system may be a viable option.
On the other hand, if there is the least doubt that a fresh installation can completely recreate
the original system environment, backing up the operating system is the best choice, even if the
backups are performed much less frequently than the backups for production data. Occasional
operating system backups also come in handy when only a few system files must be restored
(for example, due to accidental file deletion).
4. We are using the term data in this section to describe anything that is processed via backup software. This
includes operating system software, application software, as well as actual data. No matter what it is, as far as
backup software is concerned, it is all data.
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processed and stored by a typical computer system. Notice that some of the
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