I don't understand why disabling ZFS prefetch solved this
problem. The test case was a single threaded sequential write, followed
by a single threaded sequential read.
Anyone listening on ZFS have an explanation as to why disabling
prefetch solved Roland's very poor bandwidth problem?
My only thoughy here is you were tripping over a bug in
the prefetch code. I'm investigating that now.
Thanks,
/jim
roland wrote:
Hello Ben,
If you want to put this to the test, consider disabling prefetch and
trying again. See
http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide
i should have read and follow advice better - this was the essential hint.
thanks very much.
after issuing
echo zfs_prefetch_disable/W0t1 | mdb -kw
the problem immediately went away !
so, why does solaris have such stupid default set ?
is my workload that special? i cannot believe that i`m the only one with this
problem or the only one using zfs for backing up large files....
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