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NetBackup System Administrator’s Guide - Windows NT Server
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Guidelines for Setting Backup Frequency
Choose the backup frequency based on how often you must back up your files
to ensure that you can restore critical changes in case of a disk failure. How
often the data changes is an important factor in determining backup frequency.
For example, determine if files change several times a day, daily, weekly, or
monthly. Determine the rate of change by analyzing typical file usage.
Typically, sites perform daily backups to preserve each day’s work. This
ensures that, at most, only one day’s work is lost in case of a disk failure. More
frequent backups are necessary when data changes many times during the day
and these changes are important and difficult to reconstruct.
Daily backups are usually incrementals that record the changes since the last
incremental or full backup. This conserves resources because incrementals use
less storage and take less time to perform than full backups.
Full backups usually occur less frequently than incrementals but should occur
often enough to avoid accumulating too many consecutive incrementals. Too
many incrementals between full backups increases restoration time because of
the effort required to merge those incrementals when restoring files and
directories. When setting the frequency for full backups:
• Choose longer times between full backups for files that seldom change. This
uses fewer system resources. It also does not significantly increase recovery
time because there should be smaller incremental backups.
• Choose shorter times between full backups for files that change frequently.
This decreases restore time. It can also use less resources because it reduces
the cumulative effect of the longer incrementals that are necessary to keep
up with frequent changes in the files.
To achieve the most efficient use of resources, ensure that most of the files in a
given class change at about the same rate. For example, assume that about half
the files in a class file list change frequently enough to require a full backup
every week, but the rest rarely change and require only monthly full backups.
Here, if all the files are in the same class, you must perform full backups
weekly on all the files. This wastes system resources and media because half
the files need full backups only once a month. A better approach is to divide
them into two classes, each with the appropriate backup schedule.
NetBackup 3.2 System Administrator's Guide for Windows NT
NetBackup 3.2 System Administrator's Guide for Windows NT