On Tue, 14 Feb 2012, Richard Elling wrote:
Hi Andy
On Feb 14, 2012, at 10:37 AM, andy thomas wrote:
On one of our servers, we have a RAIDz1 ZFS pool called 'maths2' consisting of
7 x 300 Gb disks which in turn contains a single ZFS filesystem called 'home'.
Yesterday, using the 'ls' command to list the directories within this pool
caused the command to hang for a long period period followed by an 'i/o error'
message. 'zpool status -x maths2' reports the pool is healthy but 'iostat -en'
shows a rather different story:
root@e450:~# iostat -en
---- errors ---
s/w h/w trn tot device
0 0 0 0 fd0
0 0 0 0 c2t3d0
0 0 0 0 c2t0d0
0 0 0 0 c2t1d0
0 0 0 0 c5t3d0
0 0 0 0 c4t0d0
0 0 0 0 c4t1d0
0 0 0 0 c2t2d0
0 0 0 0 c4t2d0
0 0 0 0 c4t3d0
0 0 0 0 c5t0d0
0 0 0 0 c5t1d0
0 0 0 0 c8t0d0
0 0 0 0 c8t1d0
0 0 0 0 c8t2d0
0 503 1658 2161 c9t0d0
0 2515 6260 8775 c9t1d0
0 0 0 0 c8t3d0
0 492 2024 2516 c9t2d0
0 444 1810 2254 c9t3d0
0 0 0 0 c5t2d0
0 1 0 1 rmt/2
Obviously it looks like controller c9 or the cabling associated with it is in
trouble (the server is an Enterprise 450 with multiple disk controllers). On
taking the server down and running the 'probe-scsi-all' command from the OBP,
one disk c9t1d0 was reported as being faulty (no media present) but the others
seemed fine.
We see similar symptoms when a misbehaving disk (usually SATA) disrupts the
other disks in the same fault zone.
OK, I will replace the disk.
After booting back up, I started scrubbing the maths2 pool and for a long time,
only disk c9t1d0 reported it was being repaired. After a few hours, another
disk on this controller reported being repaired:
NAME STATE READ WRITE CKSUM
maths2 ONLINE 0 0 0
raidz1-0 ONLINE 0 0 0
c5t2d0 ONLINE 0 0 0
c5t3d0 ONLINE 0 0 0
c8t3d0 ONLINE 0 0 0
c9t0d0 ONLINE 0 0 0 21K repaired
c9t1d0 ONLINE 0 0 0 938K repaired
c9t2d0 ONLINE 0 0 0
c9t3d0 ONLINE 0 0 0
errors: No known data errors
Now, does this point to a controller/cabling/backplane problem or could all 4 disks
on this controller have been corrupted in some way? The O/S is Osol snv_134 for
SPARC and the server has been up & running for nearly a year with no problems
to date - there are two other RAIDz1 pools on this server but these are working
fine.
Not likely. More likely the faulty disk causing issues elsewhere.
It sems odd that 'zpool status' is not reporting a degraded status and
'zpool status -x' is still saying "all pools are healthy". This is a
little worrying as I use remote monitoring to keep an eye on all the
servers I admin (many of which run Solaris, OpenIndiana and FreeBSD) and
one thing that is checked every 15 minutes is the pool status using 'zpool
status -x'. But this seems to result in a false sense of security and I
could be blissfully unaware that half a pool has dropped out!
NB, for file and RAID systems that do not use checksums, such corruptions
can be catastrophic. Yea ZFS!
Yes indeed!
cheers, Andy
---------------------------------
Andy Thomas,
Time Domain Systems
Tel: +44 (0)7866 556626
Fax: +44 (0)20 8372 2582
http://www.time-domain.co.uk
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