RE: RAID failure with READ_DMA status=51 - how to avoid again?


-----Original Message-----
From: owner-freebsd-questions@xxxxxxxxxxx [mailto:owner-freebsd-
questions@xxxxxxxxxxx] On Behalf Of Oliver Iberien
Sent: Thursday, 1 March 2007 10:02 AM
To: freebsd-questions@xxxxxxxxxxx
Subject: RAID failure with READ_DMA status=51 - how to avoid again?

I would like to RAID my system but am wondering if I am asking for
trouble,
given that I got some kind of read failure error followed by file
system
corruption the first time I did it. Would it be reasonable for me to
try
RAIDing again, and if so, under what conditions? Details are as
follows:

I moved my home FreeBSD 6.0 system, which had previously been on a
single
IDE
drive, onto two SATA drives (set to 3.0 G) in a RAID-1 array, with
hardware
raid (Nvidia) on the motherboard (ASUS A8N-E). I used dump as
instructed
in
the FreeBSD FAQ. This went okay.

I then installed a third, large (400GB) SATA drive and backed up the
system on
the RAID (minus /proc, /tmp, and so on) to it using rdiff-backup. This
seemed
to go OK.

Then, when I shut down immediately afterwards, I saw this:
Feb 27 08:43:19 bsd kernel: ad8: FAILURE - READ_DMA
status=51<READY,DSC,ERROR>
error=40<UNCORRECTABLE> LBA=146193935
Feb 27 08:43:19 bsd kernel: ar0: WARNING - mirror protection lost.
RAID1
array
in DEGRADED mode
Feb 27 08:43:19 bsd kernel: ar0: writing of nVidia MediaShield
metadata is
NOT
supported yet

I rebooted, the message from the bios that the RAID was healthy came
up,
but
FreeBSD said the file system was not healthy, and I had to run fsck
about
five times for it to come up clean. The system booted to desktop,
crashed
after about ten seconds, rebooted, and turned up with a dirty
filesytem
again.

I have since dismantled RAID, removed one of the SATA drives, fsck'ed
repeatedly, and then reinstalled KDE, figuring that that as it only
crashed
when it had finished loading the desktop, that something might be
amiss
there. The system is running again.

All the drives are brand new, as is the cabling. The drives show up in
messages as "SATA150" (is 3.0G not supported in FreeBSD?), although
the
board
supports 3.0G transfer rates. There is an errata *** in the
motherboard
manual with a matrix indicating on which drive, given multiple SATA
drives,
the OS should be installed. It's silent on why this is advised and on
the
subject of the proper order if RAID is involved. Extended offline
SMART
test
on the current drive with smartctl completed without error and
overall-
health
self-assessment test result: PASSED. Thanks in advance for any advice.

Oliver

I would suggest downloading FreeSBIE, booting from it and running a dd
on your drives to see if it picks up any bad sectors:

dd if=/dev/adN of=/dev/null bs=1m conv=noerror

Regards,
Russell Wood


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