On 11/6/2012 6:36 PM, Stephen Thompson wrote:
>
> A quick test of this scenario seems to work.
> Leaving "Prefer Mounted Volumes = yes" (default).
> Setting both drives in autochanger to have 1/2 of the the total
> concurrently limit.  This per device setting seems to allow for multiple
> drives using the same Pool.

Yes, that allows more than one job to be concurrently assigned to the 
same drive. The only caveat is that data spooling should be turned on, 
otherwise data blocks from concurrent jobs will be interleaved on the 
tape. Interleaved backups are functional, but will make restores slower 
because the data blocks are not sequential. With data spooling turned 
on, only one job at a time is de-spooled to a volume, eliminating the 
interleaving at the cost of requiring disk space on the SD sufficient to 
hold the data from all concurrent jobs.

For tape, data spooling is a good idea anyway. For disk, attribute 
spooling is a good idea, but data spooling should be unnecessary. So 
this is more of a problem when using disk media.  For disk media, it is 
IMO better to set device concurrency to 1 and stagger the job start 
times. Of course, that does not scale well at all and is only viable for 
smaller installations.

>
> Not very well documented IMHO.

Well, the information is all there, but it is not necessarily all in one 
place.


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