ZFS best resilver settings?

Matthew Seaman matthew at FreeBSD.org
Thu Oct 8 07:20:34 UTC 2015

On 08/10/2015 03:43, Quartz wrote:
> (Not sure if this should be asked of -questions or -fs, I'll try here
> first)
> What's the best practice advice these days for how resilvering should be
> set, assuming that "rebuilding the array before another drive dies" is
> the only goal? Should the resilver be maxed out so it completes as fast
> as possible before another drive dies, should it be set as low as
> possible to minimize load on the other drives to reduce the chances of
> one dying, or does it matter?

That depends on what other load your server is under, and how much you
stand to lose if the server goes down.

Resilvering doesn't necessarily trigger disk failures more frequently
when done quickly as when done slowly -- if a disk spot has worn out and
will fail on next access, then resilvering will eventually reach it
however fast it runs. Ultimately, it's best to get the system back to
full resilience promptly.

The choice is between resilvering going as fast as possible vs.
resilvering having as little as possible impact on the normal
functioning of the server.  The default settings are somewhere in the
middle -- if your system will resilver in a few hours or maybe
overnight, then resist the temptation to fiddle with the settings.  On
the other hand, if it's going to take days on end, then it may be worth
while taking the temporary hit on performance and priotising resilvering
just so you can get it over with.



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