MDADM Superblock Recovery
After a power cycle I found my RAID 5 Array no longer working. I tried various methods to reassemble the array but nothing has worked so far. I believe I need to recreate the superblocks and UUIDs somehow, but was reluctant to barrel into something as to not lose a bunch of data. Thanks for reading.
Code:
cat /etc/mdadm/mdadm.conf
DEVICE partitions
ARRAY /dev/md0 level=raid5 num-devices=4 metadata=0.90 UUID=fd522a0f:2de72d76:f2afdfe9:5e3c9df1
MAILADDR root
Which is normal. It should have 4x2000GB drives (sda, sdc, sde, sdd).
Code:
cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : inactive sdd[1](S)
1953514496 blocks
unused devices: <none>
This is a problem. It only shows one drive in the array and it is also inactive. The array should have sda, sdc, and sde in there as well. When I do a `mdadm --examine /dev/sdd` everything looks fine. On the other drives examine says **no RAID superblock on /dev/sdX**.
Code:
mdadm --examine --scan
ARRAY /dev/md0 level=raid5 num-devices=4 metadata=0.90 UUID=fd522a0f:2de72d76:f2afdfe9:5e3c9df1
No help there.
Code:
mdadm --assemble --scan -v
mdadm: looking for devices for /dev/md0
mdadm: no RAID superblock on /dev/sde
mdadm: /dev/sde has wrong uuid.
mdadm: cannot open device /dev/sdd: Device or resource busy
mdadm: /dev/sdd has wrong uuid.
mdadm: no RAID superblock on /dev/sdc
mdadm: /dev/sdc has wrong uuid.
mdadm: cannot open device /dev/sdb5: Device or resource busy
mdadm: /dev/sdb5 has wrong uuid.
mdadm: no RAID superblock on /dev/sdb2
mdadm: /dev/sdb2 has wrong uuid.
mdadm: cannot open device /dev/sdb1: Device or resource busy
mdadm: /dev/sdb1 has wrong uuid.
mdadm: cannot open device /dev/sdb: Device or resource busy
mdadm: /dev/sdb has wrong uuid.
mdadm: no RAID superblock on /dev/sda
mdadm: /dev/sda has wrong uuid.
From this it looks like I have no UUIDs and no Superblocks for sda, sdc, and sde.
Code:
sudo fdisk -l
Disk /dev/sda: 2000.4 GB, 2000397852160 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907027055 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sda doesn't contain a valid partition table
Disk /dev/sdb: 250.1 GB, 250058268160 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488395055 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x353cf669
Device Boot Start End Blocks Id System
/dev/sdb1 63 476327249 238163593+ 83 Linux
/dev/sdb2 476327250 488392064 6032407+ 5 Extended
/dev/sdb5 476327313 488392064 6032376 82 Linux swap / Solaris
Disk /dev/sdc: 2000.4 GB, 2000397852160 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907027055 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sdc doesn't contain a valid partition table
Disk /dev/sdd: 2000.4 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sdd doesn't contain a valid partition table
Disk /dev/sde: 2000.4 GB, 2000397852160 bytes
255 heads, 63 sectors/track, 243201 cylinders, total 3907027055 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sde doesn't contain a valid partition table
So from this it looks like none of my RAID disks have a partition table or UUID. The closest thing I found to my problem was this thread, which suggested running `mdadm --create /dev/md0 -v -l 5 -n 4 /dev/sda /dev/sdc /dev/sde /dev/sdd` and checking for a valid filesystem with `fsck -fn /dev/md0`. However, the first command spit out `mdadm: no raid-devices specified.` I retried the command using sda1, sdc1, etc, but then I get this:
Code:
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 512K
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: super1.x cannot open /dev/sda1: No such file or directory
mdadm: ddf: Cannot open /dev/sda1: No such file or directory
mdadm: Cannot open /dev/sda1: No such file or directory
mdadm: device /dev/sda1 not suitable for any style of array
If I do a create and leave sda1 as a "missing" variable in the command then it just says the same thing for sdc1.
I am sure that I am making this more complicated than it needs to be. Can someone with experience please help me? Thanks for your time in advance.
Re: MDADM Superblock Recovery
In this thread someone suggested using the dumpe2fs tools to recover the superblock. You can still see a filesystem on the drives:
Code:
dumpe2fs /dev/sda
dumpe2fs 1.41.14 (22-Dec-2010)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: bbe6fb91-d37c-414a-8c2b-c76a30b9b5c5
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file
Filesystem flags: signed_directory_hash
Default mount options: (none)
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 366288896
Block count: 1465135872
Reserved block count: 73256793
Free blocks: 568552005
Free inodes: 366066972
First block: 0
Block size: 4096
Fragment size: 4096
Reserved GDT blocks: 674
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
Filesystem created: Wed Oct 28 12:23:09 2009
Last mount time: Tue Oct 18 13:59:36 2011
Last write time: Tue Oct 18 13:59:36 2011
Mount count: 17
Maximum mount count: 26
Last checked: Fri Oct 14 17:04:16 2011
Check interval: 15552000 (6 months)
Next check after: Wed Apr 11 17:04:16 2012
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: 17e784d8-012e-4a29-9bbd-c312de282588
Journal backup: inode blocks
Journal superblock magic number invalid!
But I don't know how to restore the superblocks and UUIDs. One place had a method using fsck but I dont want to corrupt the raid filesystem.
Re: MDADM Superblock Recovery
