A user actually ran into this in the field (RHEL 5.3) and I'm able to reproduce with: Linux vm1 2.6.30-rc8 #1 SMP Mon Jun 8 11:32:59 EDT 2009 x86_64 GNU/Linux mdadm - v2.6.7 - 6th June 2008 I'll investigate (i.e. read/debug code) when I have time but any insights would be apprecated. 1. Assemble a RAID array incorrectly (forgetting the array name): # mdadm --assemble /dev/sdb1 /dev/sdb2 /dev/sdb3 /dev/sdb4 --run mdadm: /dev/sdb1 has been started with 3 drives (out of 4). (The user did not require --run; I'm not sure why.) 2. An array is actually started. That's not so weird... # cat /proc/mdstat Personalities : [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md127 : active raid10 sdb2[1] sdb4[3] sdb3[2] 513792 blocks 64K chunks 2 near-copies [4/3] [_UUU] unused devices: <none> 3. But: # mdadm --examine /dev/sdb1 mdadm: No md superblock detected on /dev/sdb1. # mdadm --stop /dev/sdb1 mdadm: stopped /dev/sdb1 # mdadm --examine /dev/sdb1 mdadm: No md superblock detected on /dev/sdb1. # mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdb2 /dev/sdb3 /dev/sdb4 mdadm: no recogniseable superblock on /dev/sdb1 mdadm: /dev/sdb1 has no superblock - assembly aborted The problem goes away after a reboot. Cheers, Jody -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html