Date: Tue, 5 Mar 2013 09:12:47 -0000 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Jeremy Chadwick" <jdc@koitsu.org>, "Ben Morrow" <ben@morrow.me.uk> Cc: freebsd-stable@freebsd.org Subject: Re: ZFS "stalls" -- and maybe we should be talking about defaults? Message-ID: <545CD2ABE3D146F2B91963ADF6090CDE@multiplay.co.uk> References: <513524B2.6020600@denninger.net> <89680320E0FA4C0A99D522EA2037CE6E@multiplay.co.uk> <20130305050539.GA52821@anubis.morrow.me.uk> <20130305053249.GA38107@icarus.home.lan>
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----- Original Message -----
From: "Jeremy Chadwick" <jdc@koitsu.org>
To: "Ben Morrow" <ben@morrow.me.uk>
Cc: <freebsd-stable@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@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
* 8.3-RELEASE
* Pure ZFS
* Trigger MySQL doing a DB import, nothing else running.
* 4K disk alignment
Regards
Steve
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