ZFS "stalls" -- and maybe we should be talking about defaults?
killing at multiplay.co.uk
Tue Mar 5 09:13:01 UTC 2013
----- Original Message -----
From: "Jeremy Chadwick" <jdc at koitsu.org>
To: "Ben Morrow" <ben at morrow.me.uk>
Cc: <freebsd-stable at freebsd.org>
Sent: Tuesday, March 05, 2013 5:32 AM
Subject: Re: ZFS "stalls" -- and maybe we should be talking about defaults?
> On Tue, Mar 05, 2013 at 05:05:47AM +0000, Ben Morrow wrote:
>> Quoth Karl Denninger <karl at denninger.net>:
>> > Note that the machine is not booting from ZFS -- it is booting from and
>> > has its swap on a UFS 2-drive mirror (handled by the disk adapter; looks
>> > like a single "da0" drive to the OS) and that drive stalls as well when
>> > it freezes. It's definitely a kernel thing when it happens as the OS
>> > would otherwise not have locked (just I/O to the user partitions) -- but
>> > it does.
>> Is it still the case that mixing UFS and ZFS can cause problems, or were
>> they all fixed? I remember a while ago (before the arc usage monitoring
>> code was added) there were a number of reports of serious probles
>> running an rsync from UFS to ZFS.
> This problem still exists on stable/9. The behaviour manifests itself
> as fairly bad performance (I cannot remember if stalling or if just
> throughput rates were awful). I can only speculate as to what the root
> cause is, but my guess is that it has something to do with the two
> caching systems (UFS vs. ZFS ARC) fighting over large sums of memory.
In our case we have no UFS, so this isn't the cause of the stalls.
Spec here is
* 64GB RAM
* LSI 2008
* Pure ZFS
* Trigger MySQL doing a DB import, nothing else running.
* 4K disk alignment
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