scrub kills performance

[sribe]

I've googled and all I can find is people with the exact opposite problem from mine!

When I scrub my array, it proceeds about as fast as one would expect from the hardware. But performance of other applications which use the array absolutely tank. I haven't messed with default tuning parameters, so that's not it.

Code: Select all

kstat.zfs.darwin.tunable.scrub_min_active: 1
kstat.zfs.darwin.tunable.scrub_max_active: 2
kstat.zfs.darwin.tunable.zfs_scrub_limit: 0
kstat.zfs.darwin.tunable.zfs_no_scrub_io: 0
kstat.zfs.darwin.tunable.zfs_no_scrub_prefetch: 0
kstat.zfs.darwin.tunable.zfs_resilver_delay: 2
kstat.zfs.darwin.tunable.zfs_scrub_delay: 4
kstat.zfs.darwin.tunable.zfs_scan_idle: 50
kstat.zfs.darwin.tunable.zfs_recover: 0


Any way to make it be kinder to other apps needing disk I/O? I don't care if it takes a week (or even a month) to run. IIRC, I'm running 1.4.5.

[Sharko]

Well, maybe the point is that you will need to mess with the default tuning parameters in order to get what you want. It looks like scrub_delay is at the default value of 4; have you tried increasing that to 10 or 20 to see if responsiveness improves? I'm going off the descriptions on Allan Jude's ZFS page here:

http://www.allanjude.com/bsd/zfs-advanced.html

Brendon or Lundman can chime in here, but I would think that updating to latest release would be a good idea, too.

Kurt