On Thu, Aug 9, 2012 at 8:05 AM, Jummo <jummo AT devio DOT us> wrote:
>
>
> On Thu, 9 Aug 2012, John Drescher wrote:
>
>>> During the backup one copy job already run and use the first tape drive.
>>> In the output I can see that 4 Jobs runs concurrently (one was the copy
>>> job). A little bit later I noticed that 2 jobs despooling data at the
>>> same
>>> time. Will this means the jobs are mixed on the tape volume?
>>>
>>>
>
> According to [1] this should not happen:
> "...While the spooled data is being written to the tape, the despooling
> process has exclusive use of the tape. This means that you can spool
> multiple simultaneous jobs to disk, then have them very efficiently
> despooled one at a time without having the data blocks from several jobs
> intermingled, thus substantially improving the time needed to restore files.
> While despooling, all jobs spooling continue running...."
>
>
>> Yes that means the jobs will be interleaved on the same volume. Bacula
>> understands that and will have no problem restoring.
>
>
> Ok, this will end in slow restore times. It's possible to prevent this
> behaviour?
>

I have not tried to avoid this behavior so I am  not sure. I just set
my spool size to 10GB and fire off 5 jobs at once. There is some
overlap when more than 1 job is despooling to the same volume. I do
not do many restores (1 or 2 restores per year) so I have not looked
into performance ramifications of that.

John

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