Hi list,
I have a failed RAID 5 array, composed of 4 x 2TB drives without hot
spare. On the fail array, it looks like there is one drive out of sync
(the one with a lower Events counts) and another drive with a missing or
corrupted superblock (dmesg is reporting "does not have a valid v1.2
superblock, not importing!" and i have a : Checksum : 5608a55a -
expected 4108a55a).
All drives seems good though, the problem was probably triggered by a a
broken communication between the external eSATA expansion card and
external drive enclosure (card, cable or backplane in the enclosure i
guess...).
I am now in the process of making exact copies of the drives with dd to
other drives.
I have an idea on how to try to get my data back but i would be happy if
someone could help/validate with the steps i intent to follow to get
there.
On that array, i have ~ 85% of data which is already backed up somewhere
else, ~ 10% of data for which i do not care much, but there is ~ 5% of
data that is really important to me and for which i do not have other
copies around :|
So, here are the steps i intend to follow once the dd process is gonna
be over :
- take the drives which i made the dd on it
- try to create a new array on the two good drives, plus the one with
the superblock problem, by respecting the order (according to data i
have gathered from the drives), with the correct chunk size, with a
command like this :
# mdadm --create --assume-clean --level=5 --chunk=512
--raid-devices=4 /dev/md127 /dev/sdd /dev/sde /dev/sdb missing
- if the array is coming up nicely, will try to validate if fs is good
on it :
# fsck.ext4 -n /dev/md127
- if all is still fine, mount the array read-only and backup all i need
as fast as possible!
- then i guess i could add the drive (/dev/sdc) back to the array :
# mdadm --add /dev/md127 /dev/sdc
Can anyone tell me if those steps make sense? Does i miss something
obvious? Does i have any chance to recover my data with that procedure?
I would like to avoid trials and errors since it take 24 hours to make a
full copy of a drive with dd (4 days for the four drives).
Here is the output of mdadm --examine of my four drives :
/dev/sdb:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : d707f577:a9e572d5:e5d5f10c:b232f15a
Name : abc:xyz (local to host abc)
Creation Time : Fri Aug 9 21:55:47 2013
Raid Level : raid5
Raid Devices : 4
Avail Dev Size : 3907027120 (1863.02 GiB 2000.40 GB)
Array Size : 5860538880 (5589.05 GiB 6001.19 GB)
Used Dev Size : 3907025920 (1863.02 GiB 2000.40 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
Unused Space : before=1968 sectors, after=1200 sectors
State : clean
Device UUID : 2b438b47:db326d4a:0ae82357:1b88590d
Update Time : Mon Nov 10 15:48:17 2014
Checksum : ebfcf43 - correct
Events : 9370
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 2
Array State : AAA. ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdc:
Magic : a92b4efc
Version : 1.2
Feature Map : 0xa
Array UUID : d707f577:a9e572d5:e5d5f10c:b232f15a
Name : abx:xyz (local to host abc)
Creation Time : Fri Aug 9 21:55:47 2013
Raid Level : raid5
Raid Devices : 4
Avail Dev Size : 3907027120 (1863.02 GiB 2000.40 GB)
Array Size : 5860538880 (5589.05 GiB 6001.19 GB)
Used Dev Size : 3907025920 (1863.02 GiB 2000.40 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
Recovery Offset : 0 sectors
Unused Space : before=1960 sectors, after=1200 sectors
State : active
Device UUID : 011e3cbb:42c0ac0a:d6815904:2150169a
Update Time : Mon Nov 10 15:44:07 2014
Bad Block Log : 512 entries available at offset 72 sectors - bad
blocks present.
Checksum : 7ca998a5 - correct
Events : 9358
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 3
Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdd:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : d707f577:a9e572d5:e5d5f10c:b232f15a
Name : abc:xyz (local to host abc)
Creation Time : Fri Aug 9 21:55:47 2013
Raid Level : raid5
Raid Devices : 4
Avail Dev Size : 3907027120 (1863.02 GiB 2000.40 GB)
Array Size : 5860538880 (5589.05 GiB 6001.19 GB)
Used Dev Size : 3907025920 (1863.02 GiB 2000.40 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
Unused Space : before=1968 sectors, after=1200 sectors
State : clean
Device UUID : 67ffc02b:c8a013a7:3f17dc65:d1040e05
Update Time : Mon Nov 10 15:48:17 2014
Checksum : 5608a55a - expected 4108a55a
Events : 9370
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 0
Array State : AAA. ('A' == active, '.' == missing, 'R' == replacing)
/dev/sde:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : d707f577:a9e572d5:e5d5f10c:b232f15a
Name : abc:xyz (local to host abc)
Creation Time : Fri Aug 9 21:55:47 2013
Raid Level : raid5
Raid Devices : 4
Avail Dev Size : 3907027120 (1863.02 GiB 2000.40 GB)
Array Size : 5860538880 (5589.05 GiB 6001.19 GB)
Used Dev Size : 3907025920 (1863.02 GiB 2000.40 GB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
Unused Space : before=1968 sectors, after=1200 sectors
State : clean
Device UUID : 7b37a749:f1e575d1:50eea3c4:2083b9be
Update Time : Mon Nov 10 15:48:17 2014
Checksum : b6c477f4 - correct
Events : 9370
Layout : left-symmetric
Chunk Size : 512K
Device Role : Active device 1
Array State : AAA. ('A' == active, '.' == missing, 'R' == replacing)
Thanks and regards,
Tony
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