I was running a Raid5 with 3 disks at on my homeserver. But had some problems with the back-plane for the disks. The disks weren't detected reliable. So I replaced the back plane and the disks are now detected correct. But the Md array is weird broken.
When I query the physical disks with mdadm -Q /dev/sdX I get this:
root@omv:/etc/mdadm# mdadm -Q /dev/sdb
/dev/sdb: is not an md array
/dev/sdb: device 3 in 3 device unknown raid5 array. Use mdadm --examine for more detail.
root@omv:/etc/mdadm# mdadm -Q /dev/sdc
/dev/sdc: is not an md array
/dev/sdc: device 0 in 3 device unknown raid5 array. Use mdadm --examine for more detail.
root@omv:/etc/mdadm# mdadm -Q /dev/sdd
/dev/sdd: is not an md array
/dev/sdd: device 3 in 3 device unknown raid5 array. Use mdadm --examine for more detail.
Then used mdadm --examine /dev/sdX to get more information which gives me:
/dev/sdb:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : abdf672e:cf99b72d:df8be434:4b1320a7
Name : omv:pool (local to host omv)
Creation Time : Thu Oct 20 23:09:18 2011
Raid Level : raid5
Raid Devices : 3
Avail Dev Size : 3907027120 (1863.02 GiB 2000.40 GB)
Array Size : 7814051840 (3726.03 GiB 4000.79 GB)
Used Dev Size : 3907025920 (1863.02 GiB 2000.40 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
State : clean
Device UUID : b08f4b42:3d5d774b:46dd4460:10162e23
Update Time : Tue Mar 27 20:47:45 2012
Checksum : 93cc85d - correct
Events : 0
Layout : left-symmetric
Chunk Size : 512K
Device Role : spare
Array State : A.. ('A' == active, '.' == missing)
/dev/sdc:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : abdf672e:cf99b72d:df8be434:4b1320a7
Name : omv:pool (local to host omv)
Creation Time : Thu Oct 20 23:09:18 2011
Raid Level : raid5
Raid Devices : 3
Avail Dev Size : 3907027120 (1863.02 GiB 2000.40 GB)
Array Size : 7814051840 (3726.03 GiB 4000.79 GB)
Used Dev Size : 3907025920 (1863.02 GiB 2000.40 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
State : clean
Device UUID : 3a5f2e45:a00ffef6:f1881208:258c62d6
Update Time : Tue Mar 27 20:47:45 2012
Checksum : 12a86cfe - correct
Events : 246
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 0
Array State : A.. ('A' == active, '.' == missing)
/dev/sdd:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : abdf672e:cf99b72d:df8be434:4b1320a7
Name : omv:pool (local to host omv)
Creation Time : Thu Oct 20 23:09:18 2011
Raid Level : raid5
Raid Devices : 3
Avail Dev Size : 3907027120 (1863.02 GiB 2000.40 GB)
Array Size : 7814051840 (3726.03 GiB 4000.79 GB)
Used Dev Size : 3907025920 (1863.02 GiB 2000.40 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
State : clean
Device UUID : d67e800b:e5372705:556cf02d:534eb1f5
Update Time : Tue Mar 27 20:47:45 2012
Checksum : 2c50597d - correct
Events : 0
Layout : left-symmetric
Chunk Size : 512K
Device Role : spare
Array State : A.. ('A' == active, '.' == missing)
As you can see two of the three disks are marked as a spare device. Mdstat shows this:
cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md127 : inactive sdc[0](S) sdd[3](S)
3907027120 blocks super 1.2
unused devices: <none>
Running the array produces the following error:
mdadm: failed to run array /dev/md127: Input/output error
I also tried to assemble the array by hand what simple tells me that it can't create an array of two disks. Is there a way to force the spare / active state of a disk and change the disk number in the array?
