on 5-20-2009 8:32 AM Daniel Bird spake the following:

Sorry, this is going to be a rather long post...Here's the situation; I have 4 IDE disks from an old snap server which fails to mount the raid array. We believe there is a controller error on the SNAP so we've put them in another box running CentOS 5 and can see the disks OK.

hda thru hdd looks like this

Disk /dev/hdd: 185.2 GB, 185283624960 bytes 255 heads, 63 sectors/track, 22526 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System /dev/hdd1 * 1 2 16041+ 83 Linux /dev/hdd2 3 70 546210 83 Linux /dev/hdd3 71 138 546210 5 Extended /dev/hdd4 139 21781 173844468 83 Linux /dev/hdd5 71 104 273104+ 83 Linux /dev/hdd6 105 138 273104+ 83 Linux

I can mount hdX1 and hdX2 (hdx2 is xfs) on all disks.

Now /etc/raidtab (from one of the hdx2 partions) has the following entry which I'd like to re-create on the CentOS box

raiddev /dev/md0 raid-level 5 nr-raid-disks 4 nr-spare-disks 0 persistent-superblock 1 chunk-size 64 device /dev/hda4 raid-disk 0 device /dev/hdc4 raid-disk 1 device /dev/hde4 raid-disk 2 device /dev/hdg4 raid-disk 3

I've also checked the superblocks

/dev/hda4: Magic : a92b4efc Version : 00.90.00 UUID : a72e334f:a9ccba81:bba665d8:82a3c378 Creation Time : Mon Jun 30 12:00:28 2003 Raid Level : raid5 Used Dev Size : 173844352 (165.79 GiB 178.02 GB) Array Size : 521533056 (497.37 GiB 534.05 GB) Raid Devices : 4 Total Devices : 3 Preferred Minor : 0

Update Time : Tue May 19 21:40:43 2009
      State : active

Active Devices : 2 Working Devices : 2 Failed Devices : 1 Spare Devices : 0 Checksum : cbe14089 - correct Events : 0.22

     Layout : left-asymmetric
 Chunk Size : 64K

  Number   Major   Minor   RaidDevice State

this 0 3 4 0 active sync /dev/hda4

0 0 3 4 0 active sync /dev/hda4 1 1 22 4 1 faulty /dev/hdc4 2 2 0 0 2 faulty removed 3 3 34 4 3 active sync /dev/hdb4: Magic : a92b4efc Version : 00.90.00 UUID : a72e334f:a9ccba81:bba665d8:82a3c378 Creation Time : Mon Jun 30 12:00:28 2003 Raid Level : raid5 Used Dev Size : 173844352 (165.79 GiB 178.02 GB) Array Size : 521533056 (497.37 GiB 534.05 GB) Raid Devices : 4 Total Devices : 3 Preferred Minor : 0

Update Time : Sat Aug  2 19:26:28 2008
      State : active

Active Devices : 3 Working Devices : 3 Failed Devices : 0 Spare Devices : 0 Checksum : ca62ce2c - correct Events : 0.21

     Layout : left-asymmetric
 Chunk Size : 64K

  Number   Major   Minor   RaidDevice State

this 1 22 4 1 active sync /dev/hdc4

0 0 3 4 0 active sync /dev/hda4 1 1 22 4 1 active sync /dev/hdc4 2 2 0 0 2 faulty removed 3 3 34 4 3 active sync /dev/hdc4: Magic : a92b4efc Version : 00.90.00 UUID : a72e334f:a9ccba81:bba665d8:82a3c378 Creation Time : Mon Jun 30 12:00:28 2003 Raid Level : raid5 Used Dev Size : 173844352 (165.79 GiB 178.02 GB) Array Size : 521533056 (497.37 GiB 534.05 GB) Raid Devices : 4 Total Devices : 4 Preferred Minor : 0

Update Time : Sun Jul 22 22:33:00 2007
      State : active

Active Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Checksum : c871f493 - correct Events : 0.18

     Layout : left-asymmetric
 Chunk Size : 64K

  Number   Major   Minor   RaidDevice State

this 2 33 4 2 active sync

0 0 3 4 0 active sync /dev/hda4 1 1 22 4 1 active sync /dev/hdc4 2 2 33 4 2 active sync 3 3 34 4 3 active sync /dev/hdd4: Magic : a92b4efc Version : 00.90.00 UUID : a72e334f:a9ccba81:bba665d8:82a3c378 Creation Time : Mon Jun 30 12:00:28 2003 Raid Level : raid5 Used Dev Size : 173844352 (165.79 GiB 178.02 GB) Array Size : 521533056 (497.37 GiB 534.05 GB) Raid Devices : 4 Total Devices : 3 Preferred Minor : 0

Update Time : Sat Aug  2 19:26:28 2008
      State : active

Active Devices : 3 Working Devices : 3 Failed Devices : 0 Spare Devices : 0 Checksum : ca62ce3c - correct Events : 0.21

     Layout : left-asymmetric
 Chunk Size : 64K

  Number   Major   Minor   RaidDevice State

this 3 34 4 3 active sync

0 0 3 4 0 active sync /dev/hda4 1 1 22 4 1 active sync /dev/hdc4 2 2 0 0 2 faulty removed 3 3 34 4 3 active sync

This is my fist stab and re-assembling an array after moving the disks so I though I'd double check how I would go about re-assembling this Can I simply do

mdadm --assemble --scan

? Or do I need to reset the superblocks and re-assemble in degraded mode somehow?

TIA

Dan

Are you sure that all the disks are in the same position that they were in when removed from the snap server? IE... hda on the snap is still hda on the new controller. If so, you could try the assemble command. Otherwise you will have to do some creative work to get it going. But from the above superblocks, the array is very dirty, and some drives have different array status, so you might have to force things along. If this data is critical, I would dd the drives onto other hardware and experiment there, or at least dd the drives to image files and try those. If you succeed, you can backup the data and restore later. If you fail with the original drives, you might render the array unrecoverable.