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Question

Aux copy to tape backup performance issue

  • August 1, 2025
  • 1 reply
  • 63 views
Manics.mca
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Dears,

 

Initially, the auxiliary copy was running with good throughput speeds of 4000 to 5000 GB/hr. However, due to an issue with the tape drives, we recently replaced them. We deconfigured the old tape library and reconfigured the new one.

Since the new configuration, the auxiliary copy throughput has significantly dropped.

Note:
We have six LTO-6 tape drives with LTO-6 cartridges. A secondary copy has been configured, and data paths are enabled for all six drives with the associated Media Agent.

Kindly advise on how to mitigate this issue.

 

Regards,

Mani D

 

1 reply

Pasqual Döhring
Byte
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Hi.

 

I guess you are backing up the data to a disk library first? Dedupe and compression enabled?

Becaue most of the time it is not the tape library which is limiting the speed but the disk library that cannot feed the library fast enough, especially with Dedupe enabled. Since you did not change your disk library, you should look at your storage pool for the tape library and search for the multiplexing value.

In the very past the standard for multiplexing was 1. That means that you get 1 reading stream from disk to 1 tape drive. Many disk libraries won’t be fast enough to feed the tape fast enough. Then commvault changed multiplexing to 25. This sped up the auxcopy and maybe this was your last setting before you changed your configuration. Nowadays the standard setting is lower. I think it is 4, but I maybe wrong. So have a look at your multiplexing value. But keep in mind: The higher the value, the slower your restore from tape will be.

 

Best regards,

Pasqual

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