Re: mdadm RAID6 faulty drive

[Phil Turmel <philip@turmel.org>]

On 03/25/2013 12:02 PM, Paramasivam, Meenakshisundaram wrote:
> 
> Hi,
> 
> As a result of extended power outage, the FedoraCore 17 machine with
> mdadm RAID went down. Bringing it up, I noticed "faulty /dev/sdf" in
> mdadm -detail. However mdadm -E /dev/sdf shows "State : clean".
> Details are shown below. When I tried to add the drive to array,
> resync fails (I see lots of eSATA bus resets), and I get the same
> message in mdadm -detail.
> 
> Questions:
> 1. How can a clean drive be reported faulty?

When the drive is kicked out for I/O errors its superblock is left as-is
(just as if you pulled its sata cable).  The remaining devices'
superblocks are marked to show the failed drive, and *their*
superblocks' event count is bumped.  The failed status of that device is
derived during assembly when its superblock is found to be stale.

> 2. Is there a easy way to mark drive (/dev/sdf) as "assume-clean" and
> add it?

No.  The closest thing is to use a write-intent bitmap and "re-add"
devices that are disconnected.

That's not your problem.

> Please let me know if I should get an exact  replacement drive at
> this stage, pull out faulty /dev/sdf, and add the new drive to array.
> Thanks.

You very likely need a new drive.  You might want to try plugging that
drive into a different controller, or a different port on the same
controller, just to narrow the diagnosis.

You could also show us some of the kernel error messages, or show the
output of "smartctl -x /dev/sdf".

Phil