Reference Topics
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This set of schedules results in the following series of backups.
• Every other day a differential-incremental backup occurs, which will
usually have a minimum backup time.
• On alternate days, a cumulative-incremental backup occurs, which will
require more time than the differential but not as much as a full. The
differential can now be expired.
• To recover all files requires, at most, two incremental backups in addition to
the most recent full backup. This typically means less restore time than if all
differential incrementals were used. The fulls can be done less often if the
amount of data being backed up by the incrementals is small.
Determining Files Due for Backup - Windows NT Clients
On Windows NT clients, NetBackup performs incremental backups of files
based on the Perform Incrementals Based on Archive Bit setting in the
NetBackup Configuration dialog box. To open this dialog box, start the client-
user interface on the client, click Configure on the Actions menu, and go to the
General tab.
If the Perform Incrementals Based on Archive Bit box is checked, incrementals
for this client are based on the state of each file’s archive bit. The operating
system sets the bit whenever a file is changed and it remains set until cleared
by NetBackup. The conditions under which NetBackup clears the bit, depends
on the type of backup being performed.
• For a full backup, NetBackup backs up files regardless of the state of their
archive bit. After a full backup, the archive bit is always cleared.
• For a differential incremental backup, NetBackup backs up files that have
the archive bit set and have therefore been changed. When the client
receives a response from the server indicating that the backup was
successful (or partially successful) the archive bits are cleared. This allows
the next differential incremental to back up only files that have changed
since the previous full or differential-incremental backup.
day 1
day 2
day 3
day 4
day5
day 6
day 7
day 8
Full
Diff
Cum
Diff
Cum
Diff
Full
Diff
NetBackup 3.2 System Administrator's Guide for Windows NT
NetBackup 3.2 System Administrator's Guide for Windows NT
