Thanks, Darren. As a test, I disabled the other 3 drives and then ran a
backup. In this case, NetWorker just starts blasting the save sets to
tape paying no attention to the drive target sessions setting of 4, and
it doesn't ask for another tape. I think at one point it was sending as
many as 7-10 save sets there. Minimally, it did not behave as it was
before wherein it would finish 4 and then start the next 4. It was
basically just a free-for-all.
I then tried unselecting the other 3 drives from the pool resource, and
this pretty much does the same thing.
However, if I set the group parallelism to 4, regardless of whether any
of the other drives are either disabled, or unselected for the given
pool, then it keeps a steady stream of 4 save sets running at all times.
So, I guess this is how it should be acting?
George
Darren Dunham wrote:
>> Why is it that if the total number of save sets for a group exceeds the
>> value of the drive target sessions (in our case 4), and you only have
>> one writable tape, NetWorker will wait until the first 4 save sets have
>> completed before sending the next pending ones to tape?
>>
>> NetWorker does ask for a second writable tape, and yes, if I had one
>> available, it would mount it, and then it would be writing 4 save sets
>> to drive 1 and 4 to drive 2, but I don't understand why it can't start
>> sending save sets that were previously pending to drive 1 as soon as one
>> of the running save sets completes. Instead, it seems to want to wait
>> until all 4 are complete, it then pauses for a minute and then continues
>> with the next 4, and so on. Is this normal behavior? It would be nice if
>> it could send stuff there as soon as something frees up and not wait.
>
> That seems unusual to me. I can't say that I've seen that behavior.
> However, I don't think it's a setup that I've seen very often
>
> I don't know if you can do this, but it might be interesting to find if
> it does the same thing when you only have one drive available. Rather
> than having an 'up' drive with no media, can you have just one drive
> enabled?
>
> (of course since target sessions is not a hard limit, you may see many
> more than 4 streams going to the drive rather than a nice run at 4 while
> streams start and stop).
>
> When backups are limited by global or client parallelism figures, you do
> see the behavior that you are talking about. New streams begin as soon
> as one stops.
>
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