Backup

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Backups are the principle means available to provide protection to a firm's information resources from loss. It should not be considered an exaggeration to think that reliable backups are the most important product of any computer operations group.

Also see Recovery.

[edit] Reasons for doing backups

The objective of all backups is to restore a system to a good known state. There are many reasons why a backup could be needed:

  • Recover from accidental file deletions - The most common need for backups is to recover from user errors and accidents.
  • Recover from Application Errors - Bad data or processing faults may make it necessary to restore application data to a known good state.
  • Restore a Prior State of the System - Changes to the application environment such as applying patches or operating system upgrades may have a bad impact on a production system. Undoing such a change may be very tricky if it can be done at all. Performing a full backup prior to the change is good insurance that upgrade faults can be recovered.
  • Recover from Hardware Failure - Hardware faults can cause data errors or more likely crash the system. It is not unusual for interrupted processing to leave an application in an indeterminate state. Many commercial database management systems include recovery mechanisms to cleanup the mess.
  • Recover from Loss of System or Site - Commercial applications and operating environments may be recoverable from vendor media but application data and customization recovery requires a sound backup. Media should be stored off-site. If the building is destroyed it is not very helpful if all the backups were sitting in a rack next to the computer.

[edit] Backup planning

Backups should be done whenever there is a logical breakpoint in the business cycle (at the end of a business day, for example). Business requirements will dictate the time constraints around the backup window. There is almost never enough time. It is not an uncommon practice to oversimplify backups to save time, but this is almost always at the expense of recovery time, and recovery time is almost always critical.

Backup planning is nothing new, but it has grown complicated due to constant adoption to ever-changing technology. Let us see some backup strategies:

[edit] Also see