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I have /dev/md127 RAID5 array that consisted of four drives. I managed to hot remove them from the array and currently /dev/md127 does not have any drives:

cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid1 sdd1[0] sda1[1]
      304052032 blocks super 1.2 [2/2] [UU]

md1 : active raid0 sda5[1] sdd5[0]
      16770048 blocks super 1.2 512k chunks

md127 : active raid5 super 1.2 level 5, 512k chunk, algorithm 2 [4/0] [____]

unused devices: <none>


mdadm --detail /dev/md127
        Version : 1.2
  Creation Time : Thu Sep  6 10:39:57 2012
     Raid Level : raid5
     Array Size : 8790402048 (8383.18 GiB 9001.37 GB)
  Used Dev Size : 2930134016 (2794.39 GiB 3000.46 GB)
   Raid Devices : 4
  Total Devices : 0
    Persistence : Superblock is persistent

    Update Time : Fri Sep  7 17:19:47 2012
          State : clean, FAILED
 Active Devices : 0
Working Devices : 0
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 512K

    Number   Major   Minor   RaidDevice State
       0       0        0        0      removed
       1       0        0        1      removed
       2       0        0        2      removed
       3       0        0        3      removed

I've tried to do mdadm --stop /dev/md127 but:

mdadm --stop /dev/md127
mdadm: Cannot get exclusive access to /dev/md127:Perhaps a running process, mounted filesystem or active volume group?

I made sure that it's unmounted, umount -l /dev/md127 and confirmed that it indeed is unmounted:

umount /dev/md127
umount: /dev/md127: not mounted

I've tried to zero superblock of each drive and I get (for each drive):

mdadm --zero-superblock /dev/sde1
mdadm: Unrecognised md component device - /dev/sde1

Here's output of lsof|grep md127:

lsof|grep md127
md127_rai  276       root  cwd       DIR                9,0          4096          2 /
md127_rai  276       root  rtd       DIR                9,0          4096          2 /
md127_rai  276       root  txt   unknown                                             /proc/276/exe

What else can I do? LVM is not even installed so it can't be a factor.

After much poking around I finally found what was preventing me from stoping the array. It was samba process. After service smbd stop I was able to stop the array. It's strange though because although the array was mounted and shared via samba at one point in time, when I tried to stop it it was already unmounted.

share|improve this question
At this point, I think it's safe to use the --force option if you haven't tried it already. Also, what is process 276 on your system? [mdadm] ? –  Darth Android Sep 7 '12 at 15:38
It doesn't work, I get the same message: "mdadm: Cannot get exclusive access to /dev/md127:Perhaps a running process, mounted filesystem or active volume group?" –  matt Sep 7 '12 at 20:51
sudo fuser -vm /dev/md127 might show what process has a handle on the array. –  Nick Sandor Aug 3 '13 at 15:13

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