slowdown of zfs (tx->tx)
Nicolas Rachinsky
fbsd-mas-0 at ml.turing-complete.org
Thu Jan 17 09:33:06 UTC 2013
* Andriy Gapon <avg at FreeBSD.org> [2013-01-16 14:05 +0200]:
> on 16/01/2013 12:14 Steven Hartland said the following:
> > You only have ~11% free so yer it is pretty full ;-)
>
> just in case, Steve is not kidding.
>
> Those free hundreds of gigabytes could be spread over the terabytes and could be
> quite fragmented if the pool has a history of adding and removing lots of files.
> ZFS could be spending quite a lot of time in that case when it looks for some
> free space and tries to minimize further fragmentation.
>
> Empirical/anecdotal safe limit on pool utilization is said to be about 70-80%.
>
> You can test if this guess is true by doing the following:
> kgdb -w
> (kgdb) set metaslab_min_alloc_size=4096
>
> If performance noticeably improves after that, then this is your problem indeed.
I tried this, but I didn't notice any difference in performance.
Next I'll try the update Artem suggested.
Thanks
Nicolas
--
http://www.rachinsky.de/nicolas
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