Dragos wrote:
Hello,
I had created a raid 5 array on 3 232GB SATA drives. I had created one
partition (for /home) formatted with either xfs or reiserfs (I do not
recall).
Last week I reinstalled my box from scratch with Ubuntu 7.10, with
mdadm v. 2.6.2-1ubuntu2.
Then I made a rookie mistake: I --create instead of --assemble. The
recovery completed. I then stopped the array, realizing the mistake.
1. Please make the warning more descriptive: ALL DATA WILL BE LOST,
when attempting to created an array over an existing one.
2. Do you know of any way to recover from this mistake? Or at least
what filesystem it was formated with.
Any help would be greatly appreciated. I have hundreds of family
digital pictures and videos that are irreplaceable.
Thank you in advance,
Dragos
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Meh,...
I do that all the time for testing
The raid metadata is separate from the FS in that you can trash it as
much as you like and the FS it refers to will be fine as long as you
don't decide to mkfs over it
If you've an old /var/log/messages kicking around from when the raid was
correct you should be able to extract the order eg,
RAID5 conf printout:
--- rd:5 wd:5
disk 0, o:1, dev:sdf1
disk 1, o:1, dev:sde1
disk 2, o:1, dev:sdg1
disk 3, o:1, dev:sdc1
disk 4, o:1, dev:sdd1
Unfortunately, there is no point looking at mdadm -E <participating
disk> as you've already trashed the information there
Anyway From the above the recreation of the array would be
mdadm -C -l5 -n5 -c128 /dev/md0 /dev/sdf1 /dev/sde1 /dev/sdg1 /dev/sdc1
/dev/sdd1
(where -l5 = raid 5, -n5 = number of participating drives and -c128 =
chunk size of 128K)
IF you don't have the configuration printout, then you're left with
exhaustive brute force searching of the combinations
disks. Unfortunately possible combinations increase geometrically and
going beyond 8 disks is a suicidally *bad* idea
2=2
3=6
4=24
5=120
6=720
7=5040
8=40320
You only have 3 drives so only 6 possible combinations to try (unlike
myself with 5)
So, just write yourself a small script with all 6 combinations and run
them through a piece of shell similar to this pseudo script
lvchange -an /dev/VolGroup01/LogVol00 # if you use lvm at all (change as
appropriate or discard)
mdadm --stop --scan
yes | mdadm -C -l5 -n3 /dev/md0 /dev/sdd1 /dev/sde1 /dev/sdf1 #
(replaceable combinations)
lvchange -ay /dev/VolGroup01/LogVol00 # if you use lvm (or discard)
mount /dev/md0 /mnt
# Lets use the success return code for mount to indicate we're able to
mount the FS again and bail out (man mount)
if [ $? eq 0 ] ; then
exit 0
fi
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