Linux Administrator

How to Remove Raid in Linux

Recently I have created software raid 5 in Linux and mounted on a directory to store data on it. Now I want to remove Raid md device.

In this article I will show how to remove raid md device in Linux.

Remove Raid in Linux

Follow the below steps to remove the raid md device in Linux.

1. Find the below details.

Operating system  : CentOS release 6.5 (Final)
RAID device 	  : /dev/md0
		  : md0 : active raid5 sdd1[4] sdc1[3] sdb1[1] sda1[0]

As you can see I have md0 device which contain four active Disks like below.

2. Check the Raid status.

# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid5 sdd1[4] sdc1[3] sdb1[1] sda1[0]
      4189184 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
unused devices: 

[[email protected] ~]# mdadm --detail /dev/md0
        Version : 1.2
  Creation Time : Wed Apr 19 01:47:10 2017
     Raid Level : raid5
     Array Size : 4189184 (4.00 GiB 4.29 GB)
  Used Dev Size : 2094592 (2045.84 MiB 2144.86 MB)
   Raid Devices : 4
  Total Devices : 4
    Persistence : Superblock is persistent

    Update Time : Wed Apr 19 21:59:48 2017
          State : clean 
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 512K

           Name : srv6:0  (local to host srv6)
           UUID : 4e7c1751:cd467d3f:8e86a6a1:3c88f6a4
         Events : 139

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1
       3       8       33        2      active sync   /dev/sdc1
       4       8       49        3      active sync   /dev/sdd1

3. Remove RAID 5 device. First of all we should take backup of data stored in RAID device in case it needed and unmount it from filesystem like below.

# df -hTP /raid5_disk/
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/md0       ext4  5.9G  213M  5.4G   4% /raid5_disk

# umount /raid5_disk

# sed -i '/md0/d' /etc/fstab

4. Now we can stop or deactivate RAID device by running below command from root user.

# mdadm --stop /dev/md0
mdadm: stopped /dev/md0

After stopping the raid device you, can remove md device.

# mdadm --remove /dev/md0

In some OS, i find we can’t remove md device because md device is already removed after stopped with stop option as above.

# mdadm  --stop /dev/md0 
mdadm: stopped /dev/md0
# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
unused devices: 
# ls -l /dev/md0
ls: cannot access /dev/md0: No such file or directory
# mdadm  --remove /dev/md0 
mdadm: error opening /dev/md0: No such file or directory

Raid device successfully removed. Now we can Finally remove superblocks from all associated disks, like below.

#  mdadm --zero-superblock /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1
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Santosh Prasad

Hi! I'm Santosh and I'm here to post some cool article for you. If you have any query and suggestion please comment in comment section.

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