Hotplug

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 md0 RAID1 composed of /dev/sda1 and /dev/sdb1

If we hot-unplugged the disk /dev/sda, the /proc/mdstat would show:

# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda1[2](F) sdb1[1]
     3903680 blocks [2/1] [_U]
     bitmap: 0/239 pages [0KB], 8KB chunk

We see that sda1 has role [2], which is "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)