How to remove an MDADM Raid Array, Once and For All!

[NickZA]

Hi Folks

This is a short howto using mainly some info I found in the forum archives on how to completely resolve issues with not being able to kill mdadm RAID arrays, particularly when having issues with "resource/device busy" messages.
Note full kudos to the two people who made 90% of this possible, again I would have added to the original thread but sadly it was too old.

<[author: slackwarejosh]>

Alright,

I had the exact same problem today and finally figured out how to solve this.
I'll write up a n00b from the beginning in case I have to go back and find my solution later

How to remove an MDADM Raid Array

1. Find out your arrays (md0, md1, etc..) using

sudo fdisk -l

2. Query your arrays to find out what disks are contained using

sudo mdadm --detail /dev/md0
 (or md1 or whatever)

3. Shut down the array using

sudo mdadm --stop /dev/md0

4. And here's the magic key ...... zero the superblock FOR EACH drive

sudo mdadm --zero-superblock /dev/sda (or hda)
sudo mdadm --zero-superblock /dev/sdX...

I hope I helped..I am pretty new to linux and software RAID, and I never join forums, but I just started using Ubuntu and it's so darn community-centric I just had to sign up and give back.

Keep Rockin!

<[author: zaziork]>

3. Shut down the array using

sudo mdadm --stop /dev/md0

Before the above step, I needed to unmount the array first, otherwise I got the "device is busy" failure.

sudo umount /dev/md0

<[end. see original thread here http://ubuntuforums.org/showthread.php?t=394281]>

"Ok, back over to you, Nick."

One thing I just discovered in addition to the above, instead of

sudo umount /dev/md0

do

sudo umount -l /dev/md0

...This will do a lazy unmount, see man umount:

       -l     Lazy unmount. Detach the filesystem from the filesystem  hierar‐
              chy now, and cleanup all references to the filesystem as soon as
              it is not busy anymore.  (Requires kernel 2.4.11 or later.)

My circumstances were particularly troublesome due to the way I tried to delete the array with no regard for configs as though I were a Windows user or something My first disk in the array simply refused to be used in the creation of a new array although I'd cleaned up all the RAID config stuff. It claimed the resource was busy. umount -l did the trick.

Any further issues you are having with unmounting you may want to try these steps as well:

http://ubuntuforums.org/showthread.php?t=122743

Happy raiding!

-Nick

[cncook001]

To actually finish the removal of the array you also need this command

sudo mdadm --remove /dev/md0

[mikiemorales]

Thanks guys. This actually helped me a lot!

[masuch]

thanks, helped me as well.

[oldos2er]

Closed, necromancy.