Performance: changes of priority for scrub (verification)

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Performance: changes of priority for scrub (verification)

Post by grahamperrin » Sun Apr 07, 2013 5:54 am

With apologies for what may be a duplicate post …

… long, long ago I recall reading that ZEVO can automatically reduce the priority given to a scrub, if it's sensed that initial priority makes performance of the Mac too poor for the end user. And I'm almost certain that I have felt the benefits of those reductions in priority.

Can anyone recall that documentation or discussion? With keywords such as scrub and verify I have searched without success:

  • the quick start guide
  • the ZEVO home page
  • the wiki
  • this forum
  • local archives of private stuff from beta testing

– not finding what I want is a puzzle.

Maybe the automation is not specific to ZEVO, although ZFS discussions such as How to manage scrub priority or defer scrub? (2010-03) make me doubt that.

Manual changes of priority

In exceptional circumstances, after an automatic reduction, I might like to increase the priority given to a scrub …
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Post by grahamperrin » Wed Nov 13, 2013 1:38 pm

I couldn't find what I wanted for changes of priority, but I did find something else …

ZEVO CE 1.1.1 tunables
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Re: Performance: changes of priority for scrub (verification

Post by I-ku-u » Wed Nov 13, 2013 5:15 pm

I believe that explains some behavior I have observed, when writing large files to a volume/pool being scrubbed.

Specifically, I consistently notice that generating a ~7GB file over the course of an hour and writing it (as it's being generated) to a pool being scrubbed usually extends the time needed to complete the scrub by far more than the 7GB size would indicate if the performance for scrubbing were limited solely by hardware data transfer rates (and my comp is also far from CPU bound during this time).
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