2012-01-09 6:25, Richard Elling wrote:
Note: more analysis of the GPFS implementations is needed, but that will take 
more
time than I'll spend this evening :-) Quick hits below...


Good to hear you might look into it after all ;)

but at the end of the day, if we've got a 12 hour rebuild (fairly conservative 
in the days of 2TB
SATA drives), the performance degradation is going to be very real for 
end-users.

I'd like to see some data on this for modern ZFS implementations (post Summer 
2010)


Is "scrubbing performance" irrelevant in this discussion?
I think that in general, scrubbing is the read-half of
a larger rebuild process, at least for a single-vdev pool,
so rebuilds are about as long or worse. Am I wrong?

In my home-NAS case a raidz2 pool of six 2Tb drives, which
is filled 76%, consistently takes 85 hours to scrub.
No SSDs involved, no L2ARC, no ZILs. According to iostat,
the HDDs are often utilized to 100% with random IO load,
yielding from 500KBps to 2-3MBps in about 80-100IOPS per
disk (I have a scrub going on at this moment).

This system variably runs oi_148a (LiveUSB recovery) and
oi_151a when alive ;)

HTH,
//Jim Klimov
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