Veritas System Recovery 23.1 and high compression slowdown.

[JAta2]

Last month, with VSR 23.0, my complete backup with high compression took 1 hour and 15 minutes to run. Since then, I upgraded to 21.3 and this month it took 4 hours and 45 minutes to run. After investigation, I found the following:

1) I’m running the latest version of Windows 10 but do not have the latest optional update installed. My guess is next week, it or some version of it will install as a regular update.
2) Benchmarks on the destination device are unchanged (130 MB/sec writes, USB 3.0)
3) with high compression, throughput is cut to 40-50 MB/sec according to the performance monitor thus resulting in longer backup times.
4) With Standard compression, speed matches benchmark and backup completes in 2 hours.
5) The GPU does not appear to be used according to the performance monitor.
6) The source disk throughput which are all faster roughly matches the destination disk throughput as expected.

Anyone experience something like this or have a guess what is happening? Veritas support could only suggest swapping out the destination disk which makes no sense to me since it works as expected with standard compression and the benchmark times haven’t changed.

[Markus_Koestler]

Not yet.

[akihiro1 · Accepted solution]

I checked the release note for VSR 23.1. But I never find new features that are related with the performance.
https://www.veritas.com/content/support/en_US/doc/VSR_23.1_Release_Notes_EN

If many VSS shadow copies are stored in the backup source volume, the backup performance will be lower than before. Also, the performance may be lower due to fragments.

To be honest, the standard compression is the most effective for the backup time. High compression always takes more time than standard compression, and the compression rate for high compression is not high than expectation.

I recommend to use the standard compression.

[JAta2]

Thnk you, your recommendation is consistent with my findings. High compression gives me only 5% over standard and is not worth the 2-3 x duration. I had thought that perhaps VSR used the GPU to offload compression (Veritas support had indicated this was the case) but apparently not, at least not in 23.1.

[JAta2]

Additional information: Only high compression cuts the target disk rate in half. No compression, standard compression, and medium compression do not affect the target disk write rate at all. So I've adjusted my compression rate to medium for now to get the best compression without a performance penalty. I have to say I have no explanation for this. CPU utilization is low even during high compression and the GPU is not being used.