Hi,
By the mdstat shown below, you have a 3 drive raid-5 device with one spare. The
[0], [1] and [2] indicate the raid role for the associated disks. Values of [3]
or higher are the spare (for a three disk array.) In general, in an 'n' disk
raid array, [0]..[n-1] are the disks that are in the array with data, and [n]...
are the spares, as shown from /proc/mdstat.
You are in good shape for the hda2 disk to kick in as the spare if on of the
other disks fails.
<>< Lance.
Johan Ekenberg wrote:
> I recently inquired about adding a spare-disk to an operating RAID-5 array,
> and was given the advice to use raidhotadd. I've tried this and want to make
> sure that the result is the one I should expect. I thought that spare disks
> would show up as an "unused device" in /proc/mdstat, but that may not be the
> case???
>
> This is my mdstat:
> Personalities : [linear] [raid0] [raid1] [raid5]
> read_ahead 1024 sectors
> md0 : active raid5 hda2[3] sdc2[2] sdb2[1] sda2[0] 8305408 blocks level 5,
> 32k chunk, algorithm 2 [3/3] [UUU]
> unused devices: <none>
>
> The spare disk in this case is hda2[3], defined as a spare in /etc/raidtab.
> Is this the way it should look? Can I be confident that hda2 will kick in if
> one of the sd* fails? hda2 is of course formated exactly like the other
> partitions.
