On Thu, November 27, 2008 3:40 am, Greg Cormier wrote:

I have a RAID5 array of 4 disks. Was working well. I did a "yum
update" and noticed it updated mdadm to mdadm 2.6.7.1, amongst other
things (new kernel 2.2.27 instead of .26) , and now my array won't
mount.

mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1
mdadm: cannot open device /dev/sdb1: Device or resource busy
mdadm: /dev/sdb1 has no superblock - assembly aborted

[root@zeus ~]# cat /proc/mdstat
Personalities :
md_d0 : inactive sdb1[0](S) sdd1[2](S)
      976766976 blocks

unused devices: <none>


Yet, if I examine, it looks okay?

Strange.
It looks like something else tried to assemble the array and only found
sdb1 and sdd1 so it couldn't assemble it completely.  But now those
devices appear "in use" so you cannot assemble the array.
One option would be
   mdadm -S /dev/md_d0
and try again.
Another which I would like you to try is
  mdadm --incremental /dev/sdc1
  mdadm --incremental /dev/sde1

That should add those devices to the array and start it.

You didn't say what distro you were using, though as you mention "yum"
I assume a redhat based distro.  I think they might be using "--incremental"
to start arrays these days.  Maybe something when wrong somewhere.

Doug Ledford might be interested in more details.

NeilBrown