Item 1: the numerical priority of restore jobs should be dynamically set to
make them happen sooner
Date: 22 Jan, 2007
Origin: Mark Bergman
Status:
What:
If bacula is configured to run jobs concurrently, then all jobs with
a priority number less than the current job (ie., scheduled jobs that
are more important than the current job) will be allowed to run
concurrently with the current job. The lower numbered
jobs would be put at the front of the queue of the jobs that have the
current priority number. If there are several priorities involved,
then the same algorithm would apply, with lower priority numbered jobs
being effectively raised to the priority of the running job, but ordered
in the queue by their real priority.
Why: The reason for the existance of bacula (and any backup software) is
to restore data when needed. Currently, bacula's method of scheduling
prevents a restore job of greater importance (lower numerical
priority) from running at the same time as other jobs of less
importance (higher priority), even when resources (a tape drive) are
free.
An example scenario is that there a number of backups running,
including a backup of really_slow_client (using tape drive 0 in
the autochanger). All the backups are at priority 10. I attempt to
run a restore (using a tape that's already in the autochanger),
and give the restore job priority 6. Unfortunately, the restore
will not begin until all backups are complete, even when there
are idle tape drives within the autochanger. As far as I know,
even if I manually set the priority of the restore job to "10"
(matching the running backups), the restore would be executed
after the backups that are already in the queue.
Notes:
Obviously, this would be subject to resource constraints (ie, you can't
work
with two different volumes simultaneously in a single device) and to
the date/timestamp specified for job scheduling.
This change would be a tremendous improvement in managing multi-drive
storage
devices. This method of scheduling would make bacula more efficient,
allowing higher
importance (lower numerical priority) jobs to make use of physical
resources as
soon as they become available.
In some ways, this request is really a hack--the alternative (and
arguably better) method would be to change the way bacula uses
resources, so that multiple of jobs of different types & priorities
can use different physical tape drives within an autochanger at once,
but I suspect that's a much more difficult goal.
----
Mark Bergman [EMAIL PROTECTED]
System Administrator
Section of Biomedical Image Analysis 215-662-7310
Department of Radiology, University of Pennsylvania
http://pgpkeys.pca.dfn.de:11371/pks/lookup?search=mark.bergman%40.uphs.upenn.edu
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