I came to a client recently that had a large backlog of aux copy data and problematic tape libraries. After some remediation I got the tape copy running on 3 drives while awaiting replacements for a couple of broken ones. The replacements were done and following the resumption of the backup the tape copy job will only select one drive. So there are 2 media agents, each with a tape library attached, one has 3 drives and the other has 2 drives, so 5 in total. The storage policy has the 2 libraries in the path and 5 streams with multiplexing x 25. The drive pools on both libraries are set to use all drives. I cannot understand why it will only use a single drive since the backup job was resumed where it was using 3 previously. It now has 5 working drives which can all be seen in Commvault and all work fine in the Tape library GUI’s tests.Commvault version is v11.32.115.
Commvault only using one of 4 available drives
+1- Novice
Best answer by Michael Sanchez
Hello Gerard,
Mike from Commvault here, this question was brought to my attention, and I wanted to share some potential insight based on your setup.
My guess would be that there was only a single active stream remaining in the aux copy’s job queue when it was resumed, which led to only a single tape being chosen
Since the behavior of the tape library is to tie a tape and drive to a stream, even with your drives and multiplexing set up as they are, we would still only allocate a single tape drive for the job if the other 2 streams allocated to the other drives had likely written all the data they needed to.
I realize it’s unlikely the job is still running, but in the admin job history you should be able to check the Aux Copy and see how many it ran with which could confirm my theory.
Another thing that might be worth exploring is examining this behavior on your next aux copy and confirming if it runs with 3 streams at the start and dwindles as it gets closer and closer to completion.
In any case, if I am way off the mark or have missed something here, please let me know and I'll be happy to double back with you sir!
Sincerely,
Michael Sanchez
Commvault Senior Technical Enablement
- Vaulter
- Answer
Hello Gerard,
Mike from Commvault here, this question was brought to my attention, and I wanted to share some potential insight based on your setup.
My guess would be that there was only a single active stream remaining in the aux copy’s job queue when it was resumed, which led to only a single tape being chosen
Since the behavior of the tape library is to tie a tape and drive to a stream, even with your drives and multiplexing set up as they are, we would still only allocate a single tape drive for the job if the other 2 streams allocated to the other drives had likely written all the data they needed to.
I realize it’s unlikely the job is still running, but in the admin job history you should be able to check the Aux Copy and see how many it ran with which could confirm my theory.
Another thing that might be worth exploring is examining this behavior on your next aux copy and confirming if it runs with 3 streams at the start and dwindles as it gets closer and closer to completion.
In any case, if I am way off the mark or have missed something here, please let me know and I'll be happy to double back with you sir!
Sincerely,
Michael Sanchez
Commvault Senior Technical Enablement
+1- Novice
You are correct Michael, thank you. When the job resumed the percentage complete reduced which threw me off. The job did in fact finish shortly after as the bulk of the copy had already been completed.
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