ATAn timeout errors

[Robin Bowes <robin-lists@robinbowes.com>]

I posted this on the linux-ide list but got no response so I thought I'd 
try here.

My setup is as follows:

Epox EP-D3VA
Dual PIII 1GHZ processors
1.5GB RAM
Two of Promise SATA150 TX4 controllers
Six of Maxtor 250GB SATA drives (7Y250M0) - three per controller

Running Fedora Core 4 with "stock" FC4 kernel (kernel-smp-2.6.12-1.1456_FC4)

I have four md arrays as follows:

/dev/md0 RAID1 /dev/sd[ad]
/dev/md1 RAID1 /dev/sd[be]1
/dev/md2 RAID1 /dev/sd[cf]1
/dev/md5 RAID5 /dev/sd[abcef]2 (/dev/sdd2 is a hot spare)

md[0-2] are 1.5 MB areas
/dev/md0 is /
/dev/md1 is swap
/dev/md2 is currently not used

md5 is 929GB and I have used lvm to create:

/home home_lv audio_vg -wi-ao 914.38G
/usr  usr_lv  audio_vg -wi-ao  10.00G
/var  var_lv  audio_vg -wi-ao   5.00G

Ok, onto the problem...

After a couple of power outages I recently got myself a UPS but 
(typically) didn't get round to installing it before another outage (doh!).

The server came back up OK with /dev/md5 dirty and needing to resync.

However, during the re-sync, one or more of the disks clunked and I saw 
an "ATAn Timeout" message on the console and the system froze. (n 
varied, e.g. ATA2, ATA1, ATA4, etc.)  This seemed to be triggered by 
doing something that caused disk activity during the resync.

I've seen this before and done a hard-reset to start again - eventually 
the resync has completed and everything's back to normal.

However, this time, I had to drop to single-user mode and reduce the 
RAID sync speed (echo 5000 > /proc/sys/dev/raid/speed_limit_max) to get 
the resync to complete.

The server then hung again - same error - so I used Maxtor's PowerMax 
utility to perform a full test of all drives and all passed 
successfully. I then rebooted and left it re-syncing in multi-user mode 
(with fingers crossed) and this time it completed successfully.

Can anyone tell me if this is a bug somewhere or might it be a hardware 
limitation, i.e. saturating the PCI bus when resyncing? Is there 
anything I can do to prevent it from happening?

I'm not too bothered about RAID performance - I mainly use it to store 
.flac audio files which don't need great throuhgput to stream off the disk.

Any suggestions (or fixes!) appreciated.

Thanks,

R.
-- 
http://robinbowes.com

If a man speaks in a forest,
and his wife's not there,
is he still wrong?