[CentOS] CentOS 6.0 CR mdadm-3.2.2 breaks Intel BIOS RAID

Sat Oct 8 18:48:38 UTC 2011
Trey Dockendorf <treydock at gmail.com>

I just upgraded my home KVM server to CentOS 6.0 CR to make use of the
latest libvirt and now my RAID array with my VM storage is missing.  It
seems that the upgrade to mdadm-3.2.2 is the culprit.

This is the output from mdadm when scanning that array,

# mdadm --detail --scan
ARRAY /dev/md0 metadata=imsm UUID=734f79cf:22200a5a:73be2b52:3388006b
ARRAY /dev/md126 metadata=imsm UUID=3d135942:f0fad0b0:33255f78:29c3f50a
mdadm(IMSM): Unsupported attributes : 40000000
mdadm: IMSM metadata loading not allowed due to attributes incompatibility.
mdadm(IMSM): Unsupported attributes : 40000000
mdadm: IMSM metadata loading not allowed due to attributes incompatibility.
ARRAY /dev/md127 container=/dev/md0 member=0
UUID=734f79cf:22200a5a:73be2b52:3388006b

The error about IMSM shows up on google as something that happened to Fedora
users during a FC14->FC15 upgrade.

The server itself isn't old, it's a Supermicro 2U with Dual Xeon 5400 family
of CPU.  There are two RAIDs on this one controller...a RAID1 which still
functions and a RAID5 which is the one that is unable to be seen.  I don't
know what IMSM is for, but the only thing strange about that array is it is
2.7TB so the BIOS configured it as two separate arrays, one as 2TB and one
as 700GB, but it was showing up to CentOS as a single volume.

I downgraded to 3.2.1 , ran mdadm again and bam...it works,

# mdadm --detail --scan
ARRAY /dev/md0 metadata=imsm UUID=734f79cf:22200a5a:73be2b52:3388006b
ARRAY /dev/md126 metadata=imsm UUID=3d135942:f0fad0b0:33255f78:29c3f50a
ARRAY /dev/md127 container=/dev/md0 member=0
UUID=691f975d:6beecfd8:67b39886:b7ee7f6e

Hopefully this can be fixed before this version makes it to 6.1, though it's
likely a problem for upstream RHEL as well.

- Trey