ZFS w/failing drives - any equivalent of Solaris FMA?

Zaphod Beeblebrox zbeeble at gmail.com
Fri Sep 12 16:16:10 UTC 2008

On Fri, Sep 12, 2008 at 10:34 AM, Karl Pielorz <kpielorz_lst at tdx.co.uk>wrote:

> --On 12 September 2008 06:21 -0700 Jeremy Chadwick <koitsu at FreeBSD.org>
> wrote:
>  As far as I know, there is no such "standard" mechanism in FreeBSD.  If
>> the drive falls off the bus entirely (e.g. detached), I would hope ZFS
>> would notice that.  I can imagine it (might) also depend on if the disk
>> subsystem you're using is utilising CAM or not (e.g. disks should be daX
>> not adX); Scott Long might know if something like this is implemented in
>> CAM.  I'm fairly certain nothing like this is implemented in ata(4).
> For ATA, at the moment - I don't think it'll notice even if a drive
> detaches. I think like my system the other day, it'll just keep issuing I/O
> commands to the drive, even if it's disappeared (it might get much 'quicker
> failures' if the device has 'gone' to the point of FreeBSD just quickly
> returning 'fail' for every request).

Since I had the opportunity, I tested this recently for both CAM and ATA.
Now the RAID engine was gmirror in both cases (my production hardware
doesn't do ZFS yet), but I expect the reaction to be somewhat the same.

Both systems were Dell 1U's.  One, an R200, had SATA disks attached to a
plain SATA controller.  I believe it may have supported RAID1, but I didn't
use that functionality.  When a drive was removed from it, it stalled for
some time (30 minutes?) and then resumed working.  by the time I could type
on the machine again, gmirror had decided that the drive was gone and marked
the mirror as degraded.

The other system was a 1950-III with a SCSI SAS controller attached to an
SAS hot-swap backplane.  The drives themselves were 750G SATA drives.
Yanking one of them resulted in about 5 seconds of disruption followed by
gmirror realizing the problem and marking the mirror degraded.

Neither system was heavily loaded during the test.

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