[TriLUG] RAID Recover after losing 1 disk in RAID-1 setup

[Greg Cox]

> I'm not very familiar with software raid on Linux so I could not give
> him the commands he needed over the phone or via e-mail. Does anyone
> know the appropriate steps/commands to get him back on the correct
> track?

Working from memory, so, don't quote me, but.

Assuming it's hda and hdc and hda exploded/got replaced, and there
is /dev/md0 and /dev/md1 made of /dev/hdX1 and /dev/hdX2

$ cat /proc/mdstat              make sure hda shows as failed
# sfdisk -d /dev/hdc            to get the surviving drive's geometry
# fdisk /dev/hda                and proportion out the new disk similarly
# raidhotadd /dev/md0 /dev/hda1
$ watch cat /proc/mdstat        watch the rebuilding fun
# raidhotadd /dev/md1 /dev/hda2
$ watch cat /proc/mdstat        watch the rebuilding fun