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

Wood, Russell Russell.Wood at
Thu Mar 1 01:20:15 UTC 2007

> -----Original Message-----
> From: owner-freebsd-questions at [mailto:owner-freebsd-
> questions at] On Behalf Of Oliver Iberien
> Sent: Thursday, 1 March 2007 10:02 AM
> To: freebsd-questions at
> 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
> corruption the first time I did it. Would it be reasonable for me to
> RAIDing again, and if so, under what conditions? Details are as
> I moved my home FreeBSD 6.0 system, which had previously been on a
> 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
> 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.
> array
> in DEGRADED mode
> Feb 27 08:43:19 bsd kernel: ar0: writing of nVidia MediaShield
metadata is
> supported yet
> I rebooted, the message from the bios that the RAID was healthy came
> but
> FreeBSD said the file system was not healthy, and I had to run fsck
> five times for it to come up clean. The system booted to desktop,
> after about ten seconds, rebooted, and turned up with a dirty
> 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
> 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
> board
> supports 3.0G transfer rates. There is an errata sheet in the
> 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
> subject of the proper order if RAID is involved. Extended offline
> test
> on the current drive with smartctl completed without error and
> 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

Russell Wood

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