James Lee wrote:

Hi there,

I'm running a 5-drive software RAID5 array across two controllers.
The motherboard in that PC recently died - I sent the board back for
RMA.  When I refitted the motherboard, connected up all the drives,
and booted up I found that the array was being reported as degraded
(though all the data on it is intact).  I have 4 drives on the on
board controller and 1 drive on an XFX Revo 64 SATA controller card.
The drive which is being reported as not being in the array is the one
connected to the XFX controller.

The OS can see that drive fine, and "mdadm --examine" on that drive
shows that it is part of the array and that there are 5 active devices
in the array.  Doing "mdadm --examine" on one of the other four drives
shows that the array has 4 active drives and one failed.  "mdadm
--detail" for the array also shows 4 active and one failed.

Now I haven't lost any data here and I know I can just force a resync
of the array which is fine.  However I'm concerned about how this has
happened.  One worry is that the XFX SATA controller is doing
something funny to the drive.  I've noticed that it's BIOS has
defaulted to RAID0 mode (even though there's only one drive on it) - I
can't see how this would cause any particular problems here though.  I
guess it's possible that some data on the drive got corrupted when the
motherboard failed... 

I notice in your later post that the driver thinks this is a JBOD setup, 
can you either tell the controller to JBOD or force the driver to 
consider this a RAID0 single disk setup? I don't know what RAID0 on one 
drive means, but I suspect that having the controller in the mode you 
want is desirable. That might have been changed in the hardware failure.

-- 
bill davidsen [off-list ref]
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979