ZFS "stalls" -- and maybe we should be talking about defaults?

Steven Hartland 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


This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. 

In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337
or return the E.mail to postmaster at multiplay.co.uk.

More information about the freebsd-stable mailing list