I would be very grateful for advice on removing all traces of a previous
mdadm attempt to create a 3-disk RAID 5 setup so that I can try again
(or give some advice to solve the problem).
Mandriva 2010.0, mdadm v3.0.2
I had apparently created the RAID 5 set using /dev/sda, /dev/sdc,
/dev/sdd. I could write to it locally but not from the PC that has the
data I want to protect, but couldn't stop it(some message to the effect
that the devise was busy? Can't remember).
I therefore re-installed Mandriva 2010.0, used fdisk to create a single
partition on each of the three disks but was unable to create the array.
I was very surprised to find that /proc/mdstat appeared to have survived
the re-install although mdadm appears not to recognise elements of the
array (See attachment). Furthermore the existence of /dev/sda1 as a
RAID-type partition appears to cause elements of the Mandriva Control
Centre to exit abnormally (the program blkid -o udev -p /dev/sda doesn't
work).
Some RAID expertise would be very welcome!
TIA
Graeme Gemmill
# fdisk /dev/sda
Command (m for help): p
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x699d5c03
Device Boot Start End Blocks Id System
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-60801, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-60801, default 60801):
Using default value 60801
Command (m for help): t
Selected partition 1
Hex code (type L to list codes): fd
Changed system type of partition 1 to fd (Linux raid autodetect)
Command (m for help): p
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x699d5c03
Device Boot Start End Blocks Id System
/dev/sda1 1 60801 488384001 fd Linux raid autodetect
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@Bach ~]# fdisk /dev/sdc
> SNIP
Device Boot Start End Blocks Id System
/dev/sdc1 1 60801 488384001 fd Linux raid autodetect
>SNIP
[root@Bach ~]# fdisk /dev/sdd
>SNIP
Device Boot Start End Blocks Id System
/dev/sdd1 1 60801 488384001 fd Linux raid autodetect
[root@Bach ~]# mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sda1 /dev/sdc1 /dev/sdd1
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 64K
mdadm: layout defaults to left-symmetric
mdadm: super0.90 cannot open /dev/sda1: Device or resource busy
mdadm: layout defaults to left-symmetric
mdadm: super1.x cannot open /dev/sda1: Device or resource busy
mdadm: ddf: Cannot use /dev/sda1: Device or resource busy
mdadm: Cannot use /dev/sda1: It is busy
mdadm: device /dev/sda1 not suitable for any style of array
[root@Bach ~]# cat /etc/mtab
/dev/sdb2 / ext3 rw 0 0
none /proc proc rw 0 0
none /proc/sys/fs/binfmt_misc binfmt_misc rw 0 0
gvfs-fuse-daemon /home/graeme/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,user=graeme 0 0
[root@Bach ~]# cat /etc/fstab
# Entry for /dev/sdb2 :
UUID=f0c2de4f-422a-44bb-88d2-194c55dc127b / ext3 defaults 1 1
none /proc proc defaults 0 0
[root@Bach ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md127 : active raid5 sda[0] sdd[2] sdc[1]
976772992 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
unused devices: <none>
[root@Bach ~]# mdadm --stop /dev/sda
mdadm: /dev/sda does not appear to be an md device
[root@Bach ~]# mdadm --stop /dev/sdc
mdadm: /dev/sdc does not appear to be an md device
[root@Bach ~]# mdadm --zero-superblock /dev/sda1
mdadm: Couldn't open /dev/sda1 for write - not zeroing
[root@Bach ~]# mdadm --zero-superblock /dev/sda
mdadm: Couldn't open /dev/sda for write - not zeroing
[root@Bach ~]# mdadm -Q /dev/sda
/dev/sda: is not an md array
/dev/sda: device 0 in 3 device active raid5 /dev/md127. Use mdadm --examine for more detail.
[root@Bach ~]# mdadm --examine /dev/sda
/dev/sda:
Magic : a92b4efc
Version : 0.90.00
UUID : cc526422:3aae7bc9:d6030a07:261540d2
Creation Time : Wed Mar 17 15:53:39 2010
Raid Level : raid5
Used Dev Size : 488386496 (465.76 GiB 500.11 GB)
Array Size : 976772992 (931.52 GiB 1000.22 GB)
Raid Devices : 3
Total Devices : 3
Preferred Minor : 127
Update Time : Sun Mar 21 07:10:38 2010
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Checksum : 60a86cd3 - correct
Events : 50
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 0 8 0 0 active sync /dev/sda
0 0 8 0 0 active sync /dev/sda
1 1 8 32 1 active sync /dev/sdc
2 2 8 48 2 active sync /dev/sdd
[root@Bach ~]#
