--As of May 31, 2012 11:24:41 AM -0700, Dennis Glatting is alleged to have
said:
2) Under heavy I/O my systems freeze for a few seconds. I haven't looked
into why but they are completely unresponsive. Note I am also using
compressed volumes (gzip), which puts a substantual load on the kernel.
--As for the rest, it is mine.
I'm not using as huge a dataset, but I was seeing this behavior as well
when I first set my box up. What was happening was that ZFS was caching
*lots* of writes, and then would dump them all to disk at once, during
which time the computer was completely occupied with the disk I/O.
The solution (suggested from <http://wiki.freebsd.org/ZFSTuningGuide>) for
me was:
vfs.zfs.txg.timeout="5"
in loader.conf. That only allows it to cache writes for 5 seconds, instead
of the default 30. This appears to be the default in the latest versions
of FreeBSD, so if you are running an upgraded 9, ignore me. ;) (But check
the page linked above: There are other suggestions to try.)
Daniel T. Staal
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