Re: reconstruct raid superblock
From: Carl Karsten <hidden>
Date: 2009-12-17 15:06:52
I brought back the 2 externals, which have had mkfs run on them, but
maybe the extra superblocks will help (doubt it, but couldn't hurt)
root@dhcp128:/media# mdadm -E /dev/sd[a-z]
mdadm: No md superblock detected on /dev/sda.
/dev/sdb:
Magic : a92b4efc
Version : 00.90.00
UUID : 8d0cf436:3fc2d2ef:93d71b24:b036cc6b
Creation Time : Wed Mar 25 21:04:08 2009
Raid Level : raid6
Used Dev Size : 1465137408 (1397.26 GiB 1500.30 GB)
Array Size : 5860549632 (5589.06 GiB 6001.20 GB)
Raid Devices : 6
Total Devices : 6
Preferred Minor : 0
Update Time : Tue Mar 31 23:08:02 2009
State : clean
Active Devices : 5
Working Devices : 6
Failed Devices : 1
Spare Devices : 1
Checksum : a4fbb93a - correct
Events : 8430
Chunk Size : 64K
Number Major Minor RaidDevice State
this 6 8 16 6 spare /dev/sdb
0 0 8 0 0 active sync /dev/sda
1 1 8 64 1 active sync /dev/sde
2 2 8 32 2 active sync /dev/sdc
3 3 8 48 3 active sync /dev/sdd
4 4 0 0 4 faulty removed
5 5 8 80 5 active sync /dev/sdf
6 6 8 16 6 spare /dev/sdb
/dev/sdc:
Magic : a92b4efc
Version : 00.90.00
UUID : 8d0cf436:3fc2d2ef:93d71b24:b036cc6b
Creation Time : Wed Mar 25 21:04:08 2009
Raid Level : raid6
Used Dev Size : 1465137408 (1397.26 GiB 1500.30 GB)
Array Size : 5860549632 (5589.06 GiB 6001.20 GB)
Raid Devices : 6
Total Devices : 4
Preferred Minor : 0
Update Time : Sun Jul 12 11:31:47 2009
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 2
Spare Devices : 0
Checksum : a59452db - correct
Events : 580158
Chunk Size : 64K
Number Major Minor RaidDevice State
this 2 8 32 2 active sync /dev/sdc
0 0 8 0 0 active sync /dev/sda
1 1 0 0 1 faulty removed
2 2 8 32 2 active sync /dev/sdc
3 3 8 48 3 active sync /dev/sdd
4 4 0 0 4 faulty removed
5 5 8 96 5 active sync /dev/sdg
/dev/sdd:
Magic : a92b4efc
Version : 00.90.00
UUID : 8d0cf436:3fc2d2ef:93d71b24:b036cc6b
Creation Time : Wed Mar 25 21:04:08 2009
Raid Level : raid6
Used Dev Size : 1465137408 (1397.26 GiB 1500.30 GB)
Array Size : 5860549632 (5589.06 GiB 6001.20 GB)
Raid Devices : 6
Total Devices : 4
Preferred Minor : 0
Update Time : Sun Jul 12 11:31:47 2009
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 2
Spare Devices : 0
Checksum : a59452ed - correct
Events : 580158
Chunk Size : 64K
Number Major Minor RaidDevice State
this 3 8 48 3 active sync /dev/sdd
0 0 8 0 0 active sync /dev/sda
1 1 0 0 1 faulty removed
2 2 8 32 2 active sync /dev/sdc
3 3 8 48 3 active sync /dev/sdd
4 4 0 0 4 faulty removed
5 5 8 96 5 active sync /dev/sdg
/dev/sde:
Magic : a92b4efc
Version : 00.90.00
UUID : 8d0cf436:3fc2d2ef:93d71b24:b036cc6b
Creation Time : Wed Mar 25 21:04:08 2009
Raid Level : raid6
Used Dev Size : 1465137408 (1397.26 GiB 1500.30 GB)
Array Size : 5860549632 (5589.06 GiB 6001.20 GB)
Raid Devices : 6
Total Devices : 4
Preferred Minor : 0
Update Time : Sun Jul 12 11:31:47 2009
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 2
Spare Devices : 0
Checksum : a5945321 - correct
Events : 580158
Chunk Size : 64K
Number Major Minor RaidDevice State
this 5 8 96 5 active sync /dev/sdg
0 0 8 0 0 active sync /dev/sda
1 1 0 0 1 faulty removed
2 2 8 32 2 active sync /dev/sdc
3 3 8 48 3 active sync /dev/sdd
4 4 0 0 4 faulty removed
5 5 8 96 5 active sync /dev/sdg
/dev/sdf:
Magic : a92b4efc
Version : 00.90.00
UUID : 8d0cf436:3fc2d2ef:93d71b24:b036cc6b
Creation Time : Wed Mar 25 21:04:08 2009
Raid Level : raid6
Used Dev Size : 1465137408 (1397.26 GiB 1500.30 GB)
Array Size : 5860549632 (5589.06 GiB 6001.20 GB)
Raid Devices : 6
Total Devices : 5
Preferred Minor : 0
Update Time : Wed Apr 8 11:13:32 2009
State : clean
Active Devices : 5
Working Devices : 5
Failed Devices : 1
Spare Devices : 0
Checksum : a5085415 - correct
Events : 97276
Chunk Size : 64K
Number Major Minor RaidDevice State
this 1 8 80 1 active sync /dev/sdf
0 0 8 0 0 active sync /dev/sda
1 1 8 80 1 active sync /dev/sdf
2 2 8 32 2 active sync /dev/sdc
3 3 8 48 3 active sync /dev/sdd
4 4 0 0 4 faulty removed
5 5 8 96 5 active sync /dev/sdg
mdadm: No md superblock detected on /dev/sdg.
On Thu, Dec 17, 2009 at 8:39 AM, Majed B. [off-list ref] wrote:You can't copy and change bytes to identify disks. To check which disks belong to an array, do this: mdadm -E /dev/sd[a-z] The disks that you get info from belong to the existing array(s). In the first email you sent you included an examine output for one of the disks that listed another disk as a spare (sdb). The output of examine should shed more light. On Thu, Dec 17, 2009 at 5:15 PM, Carl Karsten [off-list ref] wrote:quoted
On Thu, Dec 17, 2009 at 4:35 AM, Majed B. [off-list ref] wrote:quoted
I have misread the information you've provided, so allow me to correct myself: You're running a RAID6 array, with 2 disks lost/failed. Any disk loss after that will cause data loss since you have no redundancy (2 disks died).right - but I am not sure if data loss has occurred, where data is the data being stored on the raid, not the raid metadata. My guess is I need to copy the raid superblock from one of the other disks (say sdb), find the byets that identify the disk and change from sdb to sda.quoted
I believe it's still possible to reassemble the array, but you only need to remove the MBR. See this page for information: http://www.cyberciti.biz/faq/linux-how-to-uninstall-grub/ dd if=/dev/null of=/dev/sdX bs=446 count=1 Before proceeding, provide the output of cat /proc/mdstatroot@dhcp128:~# cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] unused devices: <none>quoted
Is the array currently running degraded or is it suspended?um, not running, not sure I would call it suspended.quoted
What happened to the spare disk assigned?I don't understand.quoted
Did it finish resyncing before you installed grub on the wrong disk?I think so. I am fairly sure I could assemble the array before I installed grub.quoted
On Thu, Dec 17, 2009 at 8:21 AM, Majed B. [off-list ref] wrote:quoted
If your other disks are sane and you are able to run a degraded array, then you can remove grub using dd then re-add the disk to the array. To clear the first 1MB of the disk: dd if=/dev/zero of=/dev/sdx bs=1M count=1 Replace sdx with the disk name that has grub. On Dec 17, 2009 6:53 AM, "Carl Karsten" [off-list ref] wrote: I took over a box that had 1 ide boot drive, 6 sata raid drives (4 internal, 2 external.) I believe the 2 externals were redundant, so could be removed. so I did, and mkfs-ed them. then I installed ubuntu to the ide, and installed grub to sda, which turns out to be the first sata. which would be fine if the raid was on sda1, but it is on sda, and now the raid wont' assemble. no surprise, and I do have a backup of the data spread across 5 external drives. but before I abandon the array, I am wondering if I can fix it by recreating mdadm's metatdata on sda, given I have sd[bcd] to work with. any suggestions? root@dhcp128:~# mdadm --examine /dev/sd[abcd] mdadm: No md superblock detected on /dev/sda. /dev/sdb: Magic : a92b4efc Version : 00.90.00 UUID : 8d0cf436:3fc2d2ef:93d71b24:b036cc6b Creation Time : Wed Mar 25 21:04:08 2009 Raid Level : raid6 Used Dev Size : 1465137408 (1397.26 GiB 1500.30 GB) Array Size : 5860549632 (5589.06 GiB 6001.20 GB) Raid Devices : 6 Total Devices : 6 Preferred Minor : 0 Update Time : Tue Mar 31 23:08:02 2009 State : clean Active Devices : 5 Working Devices : 6 Failed Devices : 1 Spare Devices : 1 Checksum : a4fbb93a - correct Events : 8430 Chunk Size : 64K Number Major Minor RaidDevice State this 6 8 16 6 spare /dev/sdb 0 0 8 0 0 active sync /dev/sda 1 1 8 64 1 active sync /dev/sde 2 2 8 32 2 active sync /dev/sdc 3 3 8 48 3 active sync /dev/sdd 4 4 0 0 4 faulty removed 5 5 8 80 5 active sync 6 6 8 16 6 spare /dev/sdb /dev/sdc: Magic : a92b4efc Version : 00.90.00 UUID : 8d0cf436:3fc2d2ef:93d71b24:b036cc6b Creation Time : Wed Mar 25 21:04:08 2009 Raid Level : raid6 Used Dev Size : 1465137408 (1397.26 GiB 1500.30 GB) Array Size : 5860549632 (5589.06 GiB 6001.20 GB) Raid Devices : 6 Total Devices : 4 Preferred Minor : 0 Update Time : Sun Jul 12 11:31:47 2009 State : clean Active Devices : 4 Working Devices : 4 Failed Devices : 2 Spare Devices : 0 Checksum : a59452db - correct Events : 580158 Chunk Size : 64K Number Major Minor RaidDevice State this 2 8 32 2 active sync /dev/sdc 0 0 8 0 0 active sync /dev/sda 1 1 0 0 1 faulty removed 2 2 8 32 2 active sync /dev/sdc 3 3 8 48 3 active sync /dev/sdd 4 4 0 0 4 faulty removed 5 5 8 96 5 active sync /dev/sdd: Magic : a92b4efc Version : 00.90.00 UUID : 8d0cf436:3fc2d2ef:93d71b24:b036cc6b Creation Time : Wed Mar 25 21:04:08 2009 Raid Level : raid6 Used Dev Size : 1465137408 (1397.26 GiB 1500.30 GB) Array Size : 5860549632 (5589.06 GiB 6001.20 GB) Raid Devices : 6 Total Devices : 4 Preferred Minor : 0 Update Time : Sun Jul 12 11:31:47 2009 State : clean Active Devices : 4 Working Devices : 4 Failed Devices : 2 Spare Devices : 0 Checksum : a59452ed - correct Events : 580158 Chunk Size : 64K Number Major Minor RaidDevice State this 3 8 48 3 active sync /dev/sdd 0 0 8 0 0 active sync /dev/sda 1 1 0 0 1 faulty removed 2 2 8 32 2 active sync /dev/sdc 3 3 8 48 3 active sync /dev/sdd 4 4 0 0 4 faulty removed 5 5 8 96 5 active sync -- Carl K -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html-- Majed B.-- Carl K-- Majed B.
-- Carl K -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html