FreeBSD 8.1-R/amd64 - zfs 'hangs' - help tracing?

[Karl Pielorz]

--On 29 September 2010 08:11 -0700 Jeremy Chadwick 
<freebsd at jdc.parodius.com> wrote:

> Can you provide (with the disks hooked to an ATA/SATA controller and
> the system not wedged waiting for ZFS I/O) the output from smartctl
> (you'll probably have to install ports/sysutils/smartmontools) as:
>
> smartctl -a /dev/adXX (one command per device)
>
> I can review these statistics to see if any of the disks look like they
> may be misbehaving.
>
> It would also help if you could provide dmesg output associated with the
> ATA/SATA controller which they're hooked to.

I can do - I'll try to get all the relevant stuff up on a site and send you 
the URL  (i.e. dmesg output, zpool status output, smartctl output etc.)

The same system works fine under 7.2-Stable with the same drives, hardware 
etc. - But under 8.1 anything more than "a ZFS little I/O" (e.g. scrubs, 
copying lots of files etc.) - and it just hangs at a random point, with no 
error given - and anything that touches the zpool 'hangs next'.

I already run smartmontools - though it's currently disabled (incase it was 
that causing issues). The drives on the whole look OK, I think two have 
picked up a couple of reallocated blocks (and failed reads) - but it's 
nothing that's increasing or anything - and like I said, 7.2-S is fine with 
the same setup...

If I break to KDB with the current system, is there anything I can do to 
get a better look at what's hung up/where?

-Karl