In last two post we saw that how we could create and increase RAID 5 in Linux system.

1. Creating RAID 5 in Linux
2. How to increase existing software raid 5 storage capacity in linux

In this post we will see how we can remove RAID 5 from linux system.

Introduction

As we created software RAID 5 in Linux system and mounted in directory to store data on it. We can deactivate RAID md device and remove it.

Setup

In this setup we are using like.

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

RAID status

We have md0 device which contain four active Disks like below.

root@srv6 ~]# 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: 


[root@srv6 ~]# mdadm --detail /dev/md0
/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

Removal of 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.

[root@srv6 ~]# df -hTP /raid5_disk/
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/md0       ext4  5.9G  213M  5.4G   4% /raid5_disk
[root@srv6 ~]# umount /raid5_disk
[root@srv6 ~]# sed -i '/md0/d' /etc/fstab

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

[root@srv6 ~]# mdadm --stop /dev/md0
mdadm: stopped /dev/md0

Once you stopped 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.

[root@srv6 ~]# mdadm  --stop /dev/md0 
mdadm: stopped /dev/md0

[root@srv6 ~]# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
unused devices: 

[root@srv6 ~]# ls -l /dev/md0
ls: cannot access /dev/md0: No such file or directory

[root@srv6 ~]# mdadm  --remove /dev/md0 
mdadm: error opening /dev/md0: No such file or directory

Now we can Finally remove superblocks from all associated disks, like

[root@srv6 ~]#  mdadm --zero-superblock /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1