Neil,

You will need to change 'devices' to suite your needs.  I can run this
test with RAID 1/4/5/6 and it works, but it fails with RAID10 since
10-rc1.

thanks,
 brassow

example output:
[~]# ./md.sh 1
mdadm: /dev/sda1 appears to be part of a raid array:
    level=raid5 devices=4 ctime=Sat Jul 13 14:52:49 2013
mdadm: Note: this array has metadata at the start and
    may not be suitable as a boot device.  If you plan to
    store '/boot' on this device please ensure that
    your boot-loader understands md/v1.x metadata, or use
    --metadata=0.90
mdadm: /dev/sdb1 appears to be part of a raid array:
    level=raid5 devices=4 ctime=Sat Jul 13 14:52:49 2013
mdadm: /dev/sdc1 appears to be part of a raid array:
    level=raid5 devices=4 ctime=Sat Jul 13 14:52:49 2013
mdadm: /dev/sdd1 appears to be part of a raid array:
    level=raid5 devices=4 ctime=Sat Jul 13 14:52:49 2013
mdadm: largest drive (/dev/sda1) exceeds size (102400K) by more than 1%
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
        Waiting for resync to complete
        Waiting for resync to complete
        Waiting for resync to complete
        Waiting for resync to complete
RAID1 mismatch count after creation     : 0
mdadm: stopped /dev/md0
Writing garbage to one of the MD devices...
mdadm: /dev/md0 has been started with 4 drives.
RAID1 mismatch count after reactivation : 0
        Waiting for check to complete
        Waiting for check to complete
        Waiting for check to complete
RAID1 mismatch count after data-check   : 61440
mdadm: stopped /dev/md0


[~]# ./md.sh 10
mdadm: /dev/sda1 appears to be part of a raid array:
    level=raid1 devices=4 ctime=Mon Jul 15 10:30:44 2013
mdadm: /dev/sdb1 appears to be part of a raid array:
    level=raid1 devices=4 ctime=Mon Jul 15 10:30:44 2013
mdadm: /dev/sdc1 appears to be part of a raid array:
    level=raid1 devices=4 ctime=Mon Jul 15 10:30:44 2013
mdadm: /dev/sdd1 appears to be part of a raid array:
    level=raid1 devices=4 ctime=Mon Jul 15 10:30:44 2013
mdadm: largest drive (/dev/sda1) exceeds size (102400K) by more than 1%
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
        Waiting for resync to complete
        Waiting for resync to complete
        Waiting for resync to complete
RAID10 mismatch count after creation     : 0
mdadm: stopped /dev/md0
Writing garbage to one of the MD devices...
mdadm: /dev/md0 has been started with 4 drives.
RAID10 mismatch count after reactivation : 0
        Waiting for check to complete
        Waiting for check to complete
        Waiting for check to complete
RAID10 mismatch count after data-check   : 0
mdadm: stopped /dev/md0
***** mismatch_cnt should not be zero !!!!!!