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ScriptingSquirrel/shrink-raid-array.md

Created June 13, 2018 19:25
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Shrink existing Linux software RAID array
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shrink-raid-array.md

Current state of RAID array:

$ cat /proc/mdstat 
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md125 : active raid1 sdf4[1] sde4[0] sdg4[2]
      1922130944 blocks super 1.2 [3/3] [UUU]

unused devices: <none>

Modify RAID array /dev/md125:

# mark disk as failed and remove (`sdg4` in this example)
mdadm --fail /dev/md125 /dev/sdg4
mdadm --remove /dev/md125 /dev/sdg4

# shrink to new size
mdadm --grow --raid-devices=2 /dev/md125

Verify:

$ cat /proc/mdstat 
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md125 : active raid1 sdf4[1] sde4[0]
      1922130944 blocks super 1.2 [2/2] [UU]

unused devices: <none>
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