Disaster Recovery - Red Hat ENTERPRISE LINUX 3 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual

Chapter 8. Planning for Disaster
The important thing to do is to look at the various restoration scenarios detailed throughout this section
and determine ways to test your ability to actually carry them out. And keep in mind that the hardest
one to test is also the most critical one.
8.2.6.1. Restoring From Bare Metal
The phrase "restoring from bare metal" is a system administrator's way of describing the process of
restoring a complete system backup onto a computer with absolutely no data of any kind on it — no
operating system, no applications, nothing.
Overall, there are two basic approaches to bare metal restorations:
Reinstall, followed by restore
Here the base operating system is installed just as if a brand-new computer were being initially
set up. Once the operating system is in place and configured properly, the remaining disk drives
can be partitioned and formatted, and all backups restored from backup media.
System recovery disks
A system recovery disk is bootable media of some kind (often a CD-ROM) that contains a min-
imal system environment, able to perform most basic system administration tasks. The recovery
environment contains the necessary utilities to partition and format disk drives, the device drivers
necessary to access the backup device, and the software necessary to restore data from the backup
media.
Note
Some computers have the ability to create bootable backup tapes and to actually boot from them to
start the restoration process. However, this capability is not available to all computers. Most notably,
computers based on the PC architecture do not lend themselves to this approach.
8.2.6.2. Testing Backups
Every type of backup should be tested on a periodic basis to make sure that data can be read from it.
It is a fact that sometimes backups are performed that are, for one reason or another, unreadable. The
unfortunate part in all this is that many times it is not realized until data has been lost and must be
restored from backup.
The reasons for this can range from changes in tape drive head alignment, misconfigured backup
software, and operator error. No matter what the cause, without periodic testing you cannot be sure
that you are actually generating backups from which data can be restored at some later time.

8.3. Disaster Recovery

As a quick thought experiment, the next time you are in your data center, look around, and imagine
for a moment that it is gone. And not just the computers. Imagine that the entire building no longer
exists. Next, imagine that your job is to get as much of the work that was being done in the data center
going in some fashion, some where, as soon as possible. What would you do?
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