Well I've got it working again but I'm very confused as to *why* it
failed the way it did.
A 'cat /proc/mdstat' produced:-
Personalities : [linear] [raid0] [raid1]
md4 : active raid1 sda4[0]
973522816 blocks [2/1] [U_]
md1 : active raid1 sdb2[0] sda2[1]
256960 blocks [2/2] [UU]
md3 : active raid1 sdb3[0] sda3[1]
987904 blocks [2/2] [UU]
md2 : active raid1 sdb4[0]
973522816 blocks [2/1] [U_]
md0 : active raid1 sdb1[0] sda1[1]
1959808 blocks [2/2] [UU]
So md2 and md4 (the main parts of the two 1Tb disk drives) seemed to
be OK from the RAID point of view. But I noticed that the block
device for /dev/md4 didn't exist:-
~ # ls -l /dev/md*
brw-r----- 1 root root 9, 0 Sep 29 2011 /dev/md0
brw-r----- 1 root root 9, 1 Sep 29 2011 /dev/md1
brw-r----- 1 root root 9, 10 Sep 29 2011 /dev/md10
brw-r----- 1 root root 9, 11 Sep 29 2011 /dev/md11
brw-r----- 1 root root 9, 12 Sep 29 2011 /dev/md12
brw-r----- 1 root root 9, 13 Sep 29 2011 /dev/md13
brw-r----- 1 root root 9, 14 Sep 29 2011 /dev/md14
brw-r----- 1 root root 9, 15 Sep 29 2011 /dev/md15
brw-r----- 1 root root 9, 16 Sep 29 2011 /dev/md16
brw-r----- 1 root root 9, 17 Sep 29 2011 /dev/md17
brw-r----- 1 root root 9, 18 Sep 29 2011 /dev/md18
brw-r----- 1 root root 9, 19 Sep 29 2011 /dev/md19
brw-r----- 1 root root 9, 2 Sep 29 2011 /dev/md2
brw-r----- 1 root root 9, 20 Sep 29 2011 /dev/md20
brw-r----- 1 root root 9, 21 Sep 29 2011 /dev/md21
brw-r----- 1 root root 9, 22 Sep 29 2011 /dev/md22
brw-r----- 1 root root 9, 23 Sep 29 2011 /dev/md23
brw-r----- 1 root root 9, 24 Sep 29 2011 /dev/md24
brw-r----- 1 root root 9, 25 Sep 29 2011 /dev/md25
brw-r----- 1 root root 9, 26 Sep 29 2011 /dev/md26
brw-r----- 1 root root 9, 27 Sep 29 2011 /dev/md27
brw-r----- 1 root root 9, 28 Sep 29 2011 /dev/md28
brw-r----- 1 root root 9, 29 Sep 29 2011 /dev/md29
brw-r----- 1 root root 9, 3 Sep 29 2011 /dev/md3
brw-r----- 1 root root 9, 5 Sep 29 2011 /dev/md5
brw-r----- 1 root root 9, 6 Sep 29 2011 /dev/md6
brw-r----- 1 root root 9, 7 Sep 29 2011 /dev/md7
brw-r----- 1 root root 9, 8 Sep 29 2011 /dev/md8
brw-r----- 1 root root 9, 9 Sep 29 2011 /dev/md9
The fix was simply to use 'mknod' to create the missing /dev/md4, now
I can mount the drive and see the data.
What I don't understand is where /dev/md4 went, how would it have got
deleted? I have yet to reboot the system to see if /dev/md4
disappears again but if it does it's not a big problem to create it
again.
Should the RAID block devices get created as part of the RAID start
up? Maybe there's something gone awry there.
(Oh, and sorry for talking about SBOD when I meant JBOD)
--
Chris Green
