How do I delete a RAID volume that was created with mdadm?

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1

I created a RAID volume with mdadm on a debian system with this command:

mdadm --create --verbose /dev/md0 --level-raid6 --raid-devices=4 /dev/sdb /dev/sdc /dev/sdd /dev/sde

I am trying to delete the volume and remove the RAID data from the drives and .config file.

I’ve tried several things already:

mdadm --stop /dev/md0

This stopped the array, removed /dev/md0 but left the 4 drives with data so I can’t use them to create another RAID volume.
Other things I’ve tried:

# mdadm --query /dev/sdb
/dev/sdb: is not an md array
/dev/sdb: device 0 in 4 device unknown raid6 array.  Use mdadm --examine for more detail.

# mdadm --examine /dev/sdb
/dev/sdb:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : a40ee4c0:55d10aca:4e3bd4e0:2787cded
           Name : sp:0  (local to host sp)
  Creation Time : Mon Dec 30 08:06:16 2019
     Raid Level : raid6
   Raid Devices : 4
 Avail Dev Size : 287275936 (136.98 GiB 147.09 GB)
     Array Size : 574550016 (273.97 GiB 294.17 GB)
  Used Dev Size : 287275008 (136.98 GiB 147.08 GB)
    Data Offset : 2048 sectors
   Super Offset : 8 sectors
          State : clean
    Device UUID : eb2493a3:5cffe1fd:a8cf01d8:0065d7ba
    Update Time : Mon Dec 30 09:50:38 2019
       Checksum : 459a5384 - correct
         Events : 19
         Layout : left-symmetric
     Chunk Size : 512K
   Device Role : Active device 0
   Array State : AAAA ('A' == active, '.' == missing)

# mdadm --zero-superblock /dev/sdb
mdadm: Couldn't open /dev/sdb for write - not zeroing

# mdadm -w /dev/sdb
mdadm: /dev/sdb does not appear to be an md device

# mdadm --assemble --run md0:
mdadm: md0: not identified in config file.

# mdadm --assemble --scan
mdadm: No arrays found in config file or automatically

# ./r6_12d_b-m.sh (BASH file that creates a RAID 6 volume with 12 drives)
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 512K
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: super1.x cannot open /dev/sdb: Device or resource busy
mdadm: failed container membership check
mdadm: device /dev/sdb not suitable for any style of array

I just can’t seem to get there from here.

>:(

Help is truly appreciated!

2

Are you running these from an live cd / dvd running or from openSUSE or another running OS?

Usually you would have to:

  1. find the md and it’s components (sda, sdb, etc.)
fdisk -l
mdadm --detail /dev/md0 or md1 or mdX

after this you should have a list of the 4 drives that are in the array (maybe sdb is not in the array and you have in it sda sdc sdd and sde?)

  1. unmount the md (might be good to use the -l flag for lazy unmount
umount -l /dev/md0
  1. stop the array
mdadm --stop /dev/md0
  1. zero the superblock of **each **device from the md array
mdadm --zero-superblock /dev/sda
mdadm --zero-superblock /dev/sdX ... etc.

I do not understand why sdb was busy… did you check if the device was maybe mounted at that time?

Cheers.

3

On Thu 22 Aug 2013 07:16:02 PM CDT, JibsMan wrote:

I created a RAID volume with mdadm on a debian system with this command:

mdadm --create --verbose /dev/md0 --level-raid6 --raid-devices=4 /dev/sdb /dev/sdc /dev/sdd /dev/sde

I just can’t seem to get there from here.

:frowning:

Help is truly appreciated!

Hi
So if you run;


fdisk -l /dev/sdb

Does it show as type RAID?

I would imagine you should just offline the raid device (sdb) first,
then remove from the array, not just kill off md0…

Do you need the data on the array? If not fdisk, delete the partitions
and re-create type should be enough to turn them back into normal drives…

–
Cheers Malcolm °¿° (Linux Counter #276890)
openSUSE 12.3 (x86_64) Kernel 3.7.10-1.16-desktop
up 19:09, 3 users, load average: 0.34, 0.23, 0.20
CPU AMD E2-1800@1.70GHz | GPU Radeon HD 7340

4

Thanks for the replies. I had to remove the drives and install them in a Windows system and used the RAID card in that system to clean the drives. Returned the drives to the Linux system and I could use them again. The Linux system did not have a HW RAID card. :stuck_out_tongue:

5

That is because it has mdadm.

To remove a RAID device:

mdadm /dev/md? --fail detached --remove detached

(Copied from the man page.)