8.0-RELEASE: disk IO temporarily hangs up (ZFS or ATA related problem)

[Jeremy Chadwick]

On Wed, Dec 16, 2009 at 11:59:31AM +0300, Alexander Zagrebin wrote:
> {snip}
> 
> There are no ata error messages neither in the system log, nor on the
> console.  The manufacture's diagnostic test is passed on ad6 without
> any errors.  The ad6 also contains swap partition.  I have tried to
> run several (10..20) instances of dd, which read and write data from
> and to the swap partition simultaneously, but it has not called the
> lockup.  So there is a probability that this problem is ZFS related.
> 
> I have been forced to switch ad6 to the offline state... :(
> 
> Any suggestions on this problem?

My first guess would be that yes, this is a sign of something ZFS is
doing, but I'm not positive.  It'd be useful to see "zpool status"
output from your system (when ad6 is in the ONLINE state).

Have you tried doing "zpool scrub <pool>" to make sure there's no read,
write, or checksum errors causing problems behind the scenes?  I don't
know how this would manifest itself in that manner, but worth a shot.

Otherwise, if you could install sysutils/smartmontools and provide the
full output of "smartctl -a /dev/ad6" I'll be happy to perform a brief
analysis of the drive itself and if it's performing badly or oddly.
Please note that SMART stats don't keep track of anything pertaining to
the drive's on-PCB cache (which could be going bad, but you'd almost
certainly see that at all times not, occasionally).

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