Dan Naumov wrote:
Hello
I am having a slight issue (and judging by Google results, similar
issues have been seen by other FreeBSD and Solaris/OpenSolaris users)
with writes choking the read IO. The issue I am having is described
pretty well here:
http://opensolaris.org/jive/thread.jspa?threadID=106453 It seems that
under heavy write load, ZFS likes to aggregate a really huge amount of
data before actually writing it to disks, resulting in sudden 10+
second stalls where it frantically tries to commit everything,
completely choking read IO in the process and sometimes even the
network (with a large enough write to a mirror pool using DD, I can
cause my SSH sessions to drop dead, without actually running out of
RAM. As soon as the data is committed, I can reconnect back).
Mostly a wild guess, but can you test if this patch will help with
choking your network and ssh:
http://people.freebsd.org/~ivoras/diffs/spa.c.diff
?
You can then fiddle with the vfs.zfs.zio_worker_threads_count loader
tunable to see if it helps more.
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