I've got a sick RAID-5 array and looking for advice on the best way to
fix it. I've Google'd the hell out of it/read the FAQ and think I know
what I need to do but I what to make sure as I'd rather not have to
restore the data from backups (as they're incomplete and would be very
time consuming)
The machine is configured as follows:
* 4 x 1 TB drives (SATA) - software RAID-5, with LVM consuming all
3TB and then ext3 on top giving 2.7 TB
* 1 x OS drive (IDE) (I actually have 1x drive with RHEL5 and
another with Ubuntu which with the newer kernel is a lot more
friendly with my motherboard)
Basically I had the machine die due to a bad motherboard and DIMM.
During a boot a disc check was performed and at 1.6% Linux performed a
"kernel panic". I re-installed the OS and I'm now trying to recovery the
RAID. it looks like I have 3x problems.
* When the original OS was installed, the OS drive was located on
/dev/hda[x]. Under the new OS (Ubuntu 10.04), its now populated at
/dev/sda[x]. The RAID was originally located on /dev/sd[abcd]/
With the OS drive in /dev/sda[x], the OS is populating the RAID at
/dev/sd[bcde]. I modified the /etc/mdadm/mdadm.conf file to
reflect this. I could probably get round this by going back to the
RHEL5 OS, but it would be nice to know how to do this.
At the moment I fixed it by modifying the /etc/mdadm/mdadm.conf file as
follows:
DEVICE /dev/sd[bcde]1
ARRAY /dev/md0 level=raid5 num-devices=4
UUID=08558923:881d9efd:464c249d:988d2ec6
* The next problem (and is my main problem) is that one of the
drives (/dev/sde) has a checksum error in the superblock. So when
the try to assemble the array, I get the following:
sudo mdadm --assemble --verbose /dev/md0
mdadm: looking for devices for /dev/md0
mdadm: /dev/sde1 is identified as a member of /dev/md0, slot 3.
mdadm: /dev/sdd1 is identified as a member of /dev/md0, slot 2.
mdadm: /dev/sdc1 is identified as a member of /dev/md0, slot 1.
mdadm: /dev/sdb1 is identified as a member of /dev/md0, slot 0.
mdadm: added /dev/sdc1 to /dev/md0 as 1
mdadm: added /dev/sdd1 to /dev/md0 as 2
mdadm: failed to add /dev/sde1 to /dev/md0: Invalid argument
mdadm: added /dev/sdb1 to /dev/md0 as 0
mdadm: /dev/md0 assembled from 3 drives - not enough to start the array
while not clean - consider --force.
/var/log/messages contains the following:
md: sde1 does not have a valid v0.90 superblock, not importing!
md: md_import_device returned -22
If I dump out the info for the drive (/dev/sde1) I see the following:
sudo mdadm --examine /dev/sde1
/dev/sde1:
Magic : a92b4efc
Version : 00.90.03
UUID : 08558923:881d9efd:464c249d:988d2ec6
Creation Time : Mon Nov 3 17:42:21 2008
Raid Level : raid5
Used Dev Size : 976759936 (931.51 GiB 1000.20 GB)
Array Size : 2930279808 (2794.53 GiB 3000.61 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Update Time : Sun Aug 15 12:33:06 2010
State : active
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Checksum : e828e258 - expected e828e260
Events : 143
Layout : left-symmetric
Chunk Size : 64K
Number Major Minor RaidDevice State
this 3 8 49 3 active sync /dev/sdd1
0 0 8 1 0 active sync /dev/sda1
1 1 8 17 1 active sync /dev/sdb1
2 2 8 33 2 active sync /dev/sdc1
3 3 8 49 3 active sync /dev/sdd1
How do I fix this? Googling seems to imply recreating the array over the
top and specify the UUID? Should I force the assemble with 3x drives?
There is also a --update which updates the metadata on the disk?
* The last problem is that I believe that one of the drives has
additional metadata. This caused Ubuntu to see an additional
partition /dev/md0lp1 in addition to /dev/md0. What is the best
way of removing it?
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