On Sun, Dec 18, 2011 at 22:00, Fajar A. Nugraha <w...@fajar.net> wrote:
> From http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide
> (or at least Google's cache of it, since it seems to be inaccessible
> now:
> "
> Keep pool space under 80% utilization to maintain pool performance.
> Currently, pool performance can degrade when a pool is very full and
> file systems are updated frequently, such as on a busy mail server.
> Full pools might cause a performance penalty, but no other issues. If
> the primary workload is immutable files (write once, never remove),
> then you can keep a pool in the 95-96% utilization range. Keep in mind
> that even with mostly static content in the 95-96% range, write, read,
> and resilvering performance might suffer.
> "
> I'm guessing that your nearly-full disk, combined with your usage
> performance, is the cause of slow down. Try freeing up some space
> (e.g. make it about 75% full), just tot be sure.

I'm aware of the guidelines you refer to, and I have had slowdowns
before due to the pool being too full, but that was in the 9x% range
and the slowdown was in the order of a few percent.

At the moment I am slightly above the recommended limit, and the
performance is currently between 1/10000 and 1/2000 of what the other
pools achieve - i.e. a few hundred kB/s versus 2GB/s on the other
pools - surely allocation above 80% cannot carry such extreme

For the record - the read/write load on the pool is almost exclusively WORM.

Best regards
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