On 8/9/12 8:28 AM, "John Drescher" <drescherjm AT gmail DOT com> wrote:


>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...."
>>
>
>BTW, I am not sure about this one. However it would not be the first
>time that someone found an incorrect statement in the manual.
>
>Although it may be that bacula writes volume files exclusively when
>spooling. Remember volumes are divided into many 1GB files unless you
>changed that.  I see that some users extend that to 5GB for LTO5
>drives.
>
>
>John

I have had multiple jobs assigned to the same tape drive.  If there is
space and none of the thresholds have been reached, the spooling jobs do
continue their spooling.  If a job B is ready to despool to tape and job A
is despooling, job B will wait its turn.  The status on the storage
changer will provide the current state of each job, including the despool
wait.  I also check the timestamps on the spool files to make sure things
are still moving along.

Patti Clark
Information International Associates, Inc.
Linux Administrator and subcontractor to:
Research and Development Systems Support Oak Ridge National Laboratory



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