Following a system reinstall (an upgrade from Scientific Linux 5.x to
to 6.x), I had a RAID1 array that I could start manually with:
> mdadm --assemble /dev/md0 /dev/sda4 /dev/sdb4
but would not start automatically on reboot. SL is a RedHat clone and
all partitions were of type "fd".
The above command worked fine and I could see all my data, but every
time I rebooted the RAID1 array wasn't there.
Encouraged by the reassuring words of the mdadm man page:
--assume-clean
Tell mdadm that the array pre-existed and is known
to be clean. It can be useful when trying to recover from a
major failure as you can be sure that no data will be affected
unless you actually write to the array.
I tried:
> mdadm --create -l 1 -n 2 -assume-clean /dev/md0 /dev/sda4 /dev/sdb4
This worked, following the usual warning about how the partitions had
previously been part of an array. But now:
> mount -r /md0 /bob
refuses to do anything even if I try:
> mount -t ext2 -r /md0 /bob
I get an error message listing various possibilities such as "bad
superblock". dmesg tells me it can't find an ext2 file system
on /dev/md0
Clearly I had misunderstood the meaning of "you can be sure that no data
will be affected unless you actually write to the array" but I'm hoping
there is still a way of accessing this unaffected data.
Thanks.
John
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