Automatic Raid question (3 HDD's)

Distro Discussion & Help
1

Hello,

By mistake, we let 3 HDD’s in the PC and installed freePBX distro 4.X. mdstat reports the following:

cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sdc1[2] sda1[0] sdb1[1]
307136 blocks super 1.0 [3/3] [UUU]

md1 : active raid1 sdc2[2] sdb2[1] sda2[0]
1048000 blocks super 1.1 [3/3] [UUU]

md2 : active raid1 sdc3[2] sdb3[1] sda3[0]
141886336 blocks super 1.1 [3/3] [UUU]
bitmap: 1/2 pages [4KB], 65536KB chunk

unused devices:

What kind of raid is that? Will it work??

Thank you,
esarant

2

raid1, just as it says, it will work but be the size of your smallest harddrive with double redundancy. You probably want raid5 though, there is no EASY way of changeing from raid1 to raid5, so I suggest you start over.

3

Quite strange but possible with mdadm (read <a href=http://forums.contribs.org/index.php?topic=48541.0>here about RAID1 Array created by a user - involuntarily I add - with mdadm using three disks - and the third disk was not inserted in the created Array as spare disk, as thought).

Normally you would set up a RAID1 Array made of two (identical) disks and the third one, if available, used as a (hot) spare disk (managed by mdadm too).

4

I cant find somewhere that it is used as a hot spare from mdadm. Thats why I asked. Nevertheless, the FreePBX GUI does not displace the 3rd one.

5

Exactly what I’m saying: that one is a RAID1 Array composed by three disks without any spare disk. That one is an uncommon “three disks mirroring” but it’s also a possible scenario permitted by mdadm (mdadm will not limit you in creating such type of Array).

Indeed you will not be able to find in your configuration the the typical “S” letter which states that a disk of the Array is the Spare disk, like below (example):

$ cat /proc/mdstat
Personalities : [raid1] [raid5] [raid4]
md0 : active raid1 sdc12 sdb1[1] sda1[0]
62464 blocks [2/2] [UU]

in which /dev/sdc is the Spare disk of /dev/md0.

Probably you could remove the third disk from the Array (degrading it) and re-add it as an hot Spare disk for the Array (you must document yourself about this procedure) OR, eventually, re-install the whole FreePBX Distro and manually creating a new RAID1 two disks Array with the third disk as Spare this during the install procedure (Expert mode).