2011-12-19 2:00, Fajar A. Nugraha 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

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.

This reminds me that I had a question :)

If I were to "reserve" space on a pool by creating a dataset
with a reservation totalling, say, 20% of all pool size -
but otherwise keep this dataset empty - would it help the
pool to maintain performance until the rest of the pool is
100% full (or the said 80% of total pool size)? Technically
the pool would always have large empty slabs, but would be
forbidden to write more than 80% of pool size...

Basically this should be equivalent for "root-reserved 5%"
on traditional FSes like UFS, EXT3, etc. Would it be indeed?

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