Hotplug

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(mdadm versions < 3.1.2)
(mdadm versions < 3.1.2)
Line 14: Line 14:
 
       224612672 blocks [2/2] [UU]
 
       224612672 blocks [2/2] [UU]
  
If we hot-unplugged the disk /dev/sda, the /proc/mdstat will show:
+
If we hot-unplug the disk /dev/sda, the /proc/mdstat will show:
  
 
  # cat /proc/mdstat
 
  # cat /proc/mdstat

Revision as of 07:14, 15 April 2010

HW issues of the disk hotplugging are described in the Hotswap chapter of theHardware issues page.

The Linux RAID supports hotplug operations fully from Hot-unplug branch of the mdadm version 3.1.2.

mdadm versions < 3.1.2

Let's have the following RAID configuration:

# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda1[0] sdb1[1]
      3903680 blocks [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
      224612672 blocks [2/2] [UU]

If we hot-unplug the disk /dev/sda, the /proc/mdstat will show:

# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda1[2](F) sdb1[1]
      3903680 blocks [2/1] [_U]

md1 : active raid1 sda2[0] sdb2[1]
      224612672 blocks [2/2] [UU]

We see that sda1 has role [2]. Since RAID1 needs only 2 components - [0] and [1], the [2] means "Spare disk". And it is (F)ailed.

What we can do is remove the failed disk:

# mdadm /dev/md3 --fail detached --remove detached
mdadm: hot removed 8:1

mdadm versions > 3.1.2

(to be finished)

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