AOC-USAS2-L8i zfs panics and SCSI errors in messages

[Jeremy Chadwick]

On Wed, Oct 26, 2011 at 11:36:44AM +0200, Karli Sj?berg wrote:
> Hi all,
> 
> I tracked down what causes the panics!
> 
> I got a tip from aragon and phoenix at the forum about
> /etc/periodic/security/100.chksetuid
> 
> And to put:
> daily_status_security_chksetuid_enable="NO"
> into /etc/periodic.conf

This is not truly the cause of the panic, it simply exacerbates it.

Many of the periodic scripts will do things like iterate over all files
on the filesystem looking for specific attributes, etc..  This tends to
stress filesystems heavily.  This isn't the only one.  :-)

> I can now run periodic daily without any panics. I?m still wondering
> about the cause of this, the explanation from the forum was that that
> phase is too demanding for multi TB systems. But I have several multi
> TB servers with FreeBSD and ZFS, and none of them has ever behaved
> this way. Besides, the panic is instantaneous, not degenerative. I
> imagine that a run like that would start out OK and then just get
> worse and worse, getting gradually slower and slower until it just
> wouldn?t cope any more and hang. This feels more like hitting a wall.
> As if it found something that is couldn?t deal with and has no choice
> but to panic immediately.

It may be possible that you have some underlying filesystem corruption
that triggers this situation.  Have you actually tried doing a "zpool
scrub" of your pools and seeing if any errors happen or if the panic
occurs there?

I'm inclined to think what you're experiencing is probably a bug or
"quirk" in the storage controller driver you're using.  There are other
drivers that have had fixes applied to them "to make them work decently
with ZFS", meaning the kind of stressful I/O ZFS puts on them results in
the controller driver behaving oddly or freaking out, case in point.  It
could also be a controller firmware bug/quirk/design issue.  Seriously.

I believe the AOC-USAS2-L8i controller has been discussed on
freebsd-stable, re: mps(4) driver problems or equivalent, but I'm not
going to CC that list given that there would be 3 cross-posted lists
involved and that is liable to upset some folks.  You should search the
mailing lists for discussion of Supermicro controllers that work
reliably with FreeBSD.

It would be worthwhile to discuss this condition on -stable, mainly with
something like "Anyone else using the AOC-USAS2-L8i reliably with ZFS?"
You get the idea.

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                   Mountain View, CA, US |
| Making life hard for others since 1977.               PGP 4BD6C0CB |