Anyone using freebsd ZFS for large storage servers?

[Daniel Staal]

--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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