On Fri, Apr 2, 2010 at 2:44 AM, Matija Nalis
<mnalis+bac...@carnet.hr<mnalis%2bbac...@carnet.hr>
> wrote:
> On Thu, Apr 01, 2010 at 08:49:43AM -0600, Robert LeBlanc wrote:
> > I have two LTO-3 drives in a changer and three LTO-3 pools. Earlier
> version
> > of Bacula would try to use an empty drive before unloading a drive when a
> > tape from a different pool was requested. I used to also be able to run
> in
> > parallel migration jobs from two different pools at the same time. Since
> > moving to 5.0.1, my second drive goes unused. Is there some change in the
> > code that prevents this behavior?
>
> I think you need to set
> Prefer Mounted Volumes = no
>
> to get old behaviour (maximum parallelism).
>
> Note however that it might lead to deadlocks (or at least, it could
> in the past... don't know if that was fixed).
>
>
Prefer Mounted Volumes = <yes|no>If the Prefer Mounted Volumes directive is
set to yes (default yes), the Storage daemon is requested to select either
an Autochanger or a drive with a valid Volume already mounted in preference
to a drive that is not ready. This means that all jobs will attempt to
append to the same Volume (providing the Volume is appropriate -- right
Pool, ... for that job). If no drive with a suitable Volume is available, it
will select the first available drive. Note, any Volume that has been
requested to be mounted, will be considered valid as a mounted volume by
another job. This if multiple jobs start at the same time and they all
prefer mounted volumes, the first job will request the mount, and the other
jobs will use the same volume.
If the directive is set to no, the Storage daemon will prefer finding an
unused drive, otherwise, each job started will append to the same Volume
(assuming the Pool is the same for all jobs). Setting Prefer Mounted Volumes
to no can be useful for those sites with multiple drive autochangers that
prefer to maximize backup throughput at the expense of using additional
drives and Volumes. This means that the job will prefer to use an unused
drive rather than use a drive that is already in use.
I guess this is where we need clarification about what is an available
drive. I took this to mean a drive that has no tape is more available, and
then a drive that does already have a tape mounted would be next in
availability. It seems that as long as no job is writing to that tape, then
the drive is available. I do want this setting to yes and not no, however, I
would like to minimize tape changes, but take advantage of the multiple
drives.
Robert LeBlanc
Life Sciences & Undergraduate Education Computer Support
Brigham Young University
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