Record first your existing setup
[root@centosprod1 ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdf1[2] sdg1[3]
1043968 blocks super 1.2 level 5, 512k chunk, algorithm 2 [2/2] [UU]
unused devices:
[root@centosprod1 ~]# mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon May 7 14:35:19 2012
Raid Level : raid5
Array Size : 1043968 (1019.67 MiB 1069.02 MB)
Used Dev Size : 1043968 (1019.67 MiB 1069.02 MB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Mon May 14 12:52:21 2012
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Name : centosprod1:0 (local to host centosprod1)
UUID : f443db62:a4ff36fd:ab0706e4:d9e299cc
Events : 104
Number Major Minor RaidDevice State
3 8 97 0 active sync /dev/sdg1
2 8 81 1 active sync /dev/sdf1
We will now add the new device /dev/sde1[root@centosprod1 ~]# mdadm --add /dev/md0 /dev/sde1 mdadm: added /dev/sde1
[root@centosprod1 ~]# mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon May 7 14:35:19 2012
Raid Level : raid5
Array Size : 1043968 (1019.67 MiB 1069.02 MB)
Used Dev Size : 1043968 (1019.67 MiB 1069.02 MB)
Raid Devices : 2
Total Devices : 3
Persistence : Superblock is persistent
Update Time : Mon May 14 13:02:13 2012
State : clean
Active Devices : 2
Working Devices : 3
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Name : centosprod1:0 (local to host centosprod1)
UUID : f443db62:a4ff36fd:ab0706e4:d9e299cc
Events : 105
Number Major Minor RaidDevice State
3 8 97 0 active sync /dev/sdg1
2 8 81 1 active sync /dev/sdf1
4 8 65 - spare /dev/sde1
The disk has been added but you would notice that it is still spare. We will now set our raid array to have 3 devices[root@centosprod1 ~]# mdadm --grow /dev/md0 --raid-devices=3 mdadm: Need to backup 1024K of critical section..
[root@centosprod1 ~]# mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon May 7 14:35:19 2012
Raid Level : raid5
Array Size : 1043968 (1019.67 MiB 1069.02 MB)
Used Dev Size : 1043968 (1019.67 MiB 1069.02 MB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Update Time : Mon May 14 13:03:28 2012
State : clean, reshaping
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Reshape Status : 8% complete
Delta Devices : 1, (2->3)
Name : centosprod1:0 (local to host centosprod1)
UUID : f443db62:a4ff36fd:ab0706e4:d9e299cc
Events : 120
Number Major Minor RaidDevice State
3 8 97 0 active sync /dev/sdg1
2 8 81 1 active sync /dev/sdf1
4 8 65 2 active sync /dev/sde1
The new disk has successfully added.[root@centosprod1 ~]# mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon May 7 14:35:19 2012
Raid Level : raid5
Array Size : 1043968 (1019.67 MiB 1069.02 MB)
Used Dev Size : 1043968 (1019.67 MiB 1069.02 MB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Update Time : Mon May 14 13:10:00 2012
State : clean, reshaping
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Reshape Status : 63% complete
Delta Devices : 1, (2->3)
Name : centosprod1:0 (local to host centosprod1)
UUID : f443db62:a4ff36fd:ab0706e4:d9e299cc
Events : 157
Number Major Minor RaidDevice State
3 8 97 0 active sync /dev/sdg1
2 8 81 1 active sync /dev/sdf1
4 8 65 2 active sync /dev/sde1
