raid6 failed due to loss of connection

Hi,

I have a raid 6 consisting of 10 drives, 2x5 sata disks. Each set of 5 behind a port multiplier. The port multipliers/disk/drivers are a bit flaky sometimes and I need to pull the cable between the controller and port multiplier to get the disks recognized sometimes.

Now after rebooting I can't assemble the array.
mdadm -A /dev/md12, reports that 5 disks are too few to assemble array.

One set of (5) disks says that everything is ok when checked with mdadm -E, but the other set says that 5 disks are failed.

The first set of 5 disks report this:

/dev/sdax2:

          Magic : a92b4efc
        Version : 1.1
    Feature Map : 0x0
     Array UUID : 557d7924:1c547f1c:d878c05d:5a37cfcd
           Name : 12

Creation Time : Sun Oct 18 22:07:52 2009
Raid Level : raid6
Raid Devices : 10

Avail Dev Size : 1953118176 (931.32 GiB 1000.00 GB)

     Array Size : 15624941568 (7450.55 GiB 7999.97 GB)

Used Dev Size : 1953117696 (931.32 GiB 1000.00 GB)
Data Offset : 264 sectors
Super Offset : 0 sectors
State : clean
Device UUID : ac9db196:fc239a13:2a44b03b:aa45055a

Update Time : Thu Nov 18 13:17:25 2010
Checksum : d65e4e57 - correct
Events : 6

Chunk Size : 256K

Array Slot : 5 (failed, failed, failed, failed, failed, 5, 6, 7, 8, 9)
Array State : _____Uuuuu 5 failed

other 5 disks report this:

/dev/sdt2:

          Magic : a92b4efc
        Version : 1.1
    Feature Map : 0x0
     Array UUID : 557d7924:1c547f1c:d878c05d:5a37cfcd
           Name : 12

Creation Time : Sun Oct 18 22:07:52 2009
Raid Level : raid6
Raid Devices : 10

Avail Dev Size : 1953118176 (931.32 GiB 1000.00 GB)

     Array Size : 15624941568 (7450.55 GiB 7999.97 GB)
  Used Dev Size : 1953117696 (931.32 GiB 1000.00 GB)
    Data Offset : 264 sectors
   Super Offset : 0 sectors
          State : clean
    Device UUID : 2bc9f9dc:efcc4041:8a495b40:ad504353

    Update Time : Sat Nov  6 14:56:15 2010
       Checksum : 482b7858 - correct
         Events : 2

     Chunk Size : 256K

    Array Slot : 0 (0, 1, 2, 3, 4, 5, 6, 7, 8, 9)

Array State : Uuuuuuuuuu

Should I try mdadm -A -f /dev/md12 or do I need to run a create command to get the array up and running?

I'm in the process of copying the drives so I have a backup in case something goes wrong with the assembling...

/Björn
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Doing a create is always the last measure to try. Forcing re-assembly is a gazillion times safer because you can't get the data-disks in wrong order.

Make sure you have the latest mdadm (3.1.4 I believe) and force-assemble the array and see if that works.

Mikael Abrahamsson    email: [email protected]