Item 1: Specify a minumum number of backups to retain
Origin: Mark Bergman <mark.berg...@uphs.upenn.edu>
Date: Mon, 30 Nov 2009
Status:
What: Add an option ("Keep Mimimum") to specify that a minimum number of
backups (per-level and per-client) should be retained, over-riding
the other retention policies. If the number of existing backups
is less than or equal to the specified minimum, then the existing
backups are not purged.
Example:
JobDefs {
Name = "DefaultJob"
Type = Backup
FileSet = "Default"
Pool = Incremental
Full Backup Pool = Full
Incremental Backup Pool = Incremental
Keep Mimimum Full = 1
Keep Minimum Differential = 1
Keep Minimum Incremental = 0
}
Those settings ("Keep Mimimum") could be specified in the per-client
job definition, which would take precedence over the default...but that
is unlikely usage.
Why: Particularly as data volumes increase, the frequency of full backups
decreases. This leads to a situation where there may be very few full
backups, run at long intervals. A failed backup or other schedule
change can result in such a long interval between jobs that the
remaining full backups are expired and purged before a new backup has
completed successfully. Without a full backup as a reference point, a
complete restoration is impossible.
This option would also alleviate the problem of incremental backups
being unexpectedly promoted to "full" because the last full backup
was purged. That promotion can be difficult to deal with if it
occurs outside of a schedule (ie., there may not be enough media
or storage space available for the backup, running full backups may
be so disruptive that they are scheduled for specific maintenance
windows, etc.).
Notes: If the mimimum number of backups to retain defaults to "0" then the
current behavior is unchanged. A setting of "1" (the recommended option
for full backups) would instruct bacula not to purge the last
remaining full backup for a client until the next backup at that level
succeeds.
This option requires no changes to the basic retention algorithm...it's
a test that would be applied after all existing retention/recycling/
purging decisions have been made, but before the action takes place.
----
Mark Bergman voice: 215-662-7310
mark.berg...@uphs.upenn.edu fax: 215-614-0266
System Administrator Section of Biomedical Image Analysis
Department of Radiology University of Pennsylvania
PGP Key: https://www.rad.upenn.edu/sbia/bergman
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