here my problem: I am running ubuntu 12.04 on a raid10 (4 disks), on top of which I installed an lvm with two volume groups (one for /, one for /home). The layout of the disks are as follows: Disk /dev/sda: 1500.3 GB, 1500301910016 bytes 255 heads, 63 sectors/track, 182401 cylinders, total 2930277168 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: 0x0003f3b6 Device Boot Start End Blocks Id System /dev/sda1 * 63 481949 240943+ 83 Linux /dev/sda2 481950 2910640634 1455079342+ fd Linux raid autodetect /dev/sda3 2910640635 2930272064 9815715 82 Linux swap / Solaris Disk /dev/sdb: 1500.3 GB, 1500301910016 bytes 255 heads, 63 sectors/track, 182401 cylinders, total 2930277168 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: 0x00069785 Device Boot Start End Blocks Id System /dev/sdb1 63 2910158684 1455079311 fd Linux raid autodetect /dev/sdb2 2910158685 2930272064 10056690 82 Linux swap / Solaris Disk /dev/sdc: 1500.3 GB, 1500301910016 bytes 255 heads, 63 sectors/track, 182401 cylinders, total 2930277168 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 Device Boot Start End Blocks Id System /dev/sdc1 63 2910158684 1455079311 fd Linux raid autodetect /dev/sdc2 2910158685 2930272064 10056690 82 Linux swap / Solaris Disk /dev/sdd: 1500.3 GB, 1500301910016 bytes 255 heads, 63 sectors/track, 182401 cylinders, total 2930277168 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: 0x000f14de Device Boot Start End Blocks Id System /dev/sdd1 63 2910158684 1455079311 fd Linux raid autodetect /dev/sdd2 2910158685 2930272064 10056690 82 Linux swap / Solaris The first disk (/dev/sda) contains the /boot partition on /dev/sda1. I use grub2 to boot the system off this partition. On top of this raid10 I installed two volume groups, one for /, one for /home. This system worked well, I even exchanged two disks during the last two years. It always worked. But not this time. For the first time, /dev/sda broke. I do not know if this is an issue – I know I would have struggled anyways to overcome the problem with /boot installed on that disk and grub2 installed on the mbr of /dev/sda. Anyways, I did what I always did: start knoppix fire up the raid sudo mdadm --examine -scan which returns ARRAY /dev/md127 UUID=0dbf4558:1a943464:132783e8:19cdff95 start it up sudo mdadm --assemble /dev/md127 fail the failing disk (smart event) sudo mdadm /dev/md127 --fail /dev/sda2 remove the failing disk sudo mdadm /dev/md127 --remove /dev/sda2 stop the raid sudo mdadm -S /dev/md127 take out the disk replace it with a new one create the same partitions as on the failling one add it to the raid sudo mdadm --assemble /dev/md127 sudo mdadm /dev/md127 --add /dev/sda2 wait 4 hours All looks fine: cat /proc/mdstat returns: Personalities : [raid10] md127 : active raid10 sda2[0] sdd1[3] sdc1[2] sdb1[1] 2910158464 blocks 64K chunks 2 near-copies [4/4] [UUUU] unused devices: <none> and sudo mdadm --detail /dev/md127 returns /dev/md127: Version : 0.90 Creation Time : Wed Jun 10 13:08:46 2009 Raid Level : raid10 Array Size : 2910158464 (2775.34 GiB 2980.00 GB) Used Dev Size : 1455079232 (1387.67 GiB 1490.00 GB) Raid Devices : 4 Total Devices : 4 Preferred Minor : 127 Persistence : Superblock is persistent Update Time : Thu Mar 21 16:27:40 2013 State : clean Active Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Layout : near=2 Chunk Size : 64K UUID : 0dbf4558:1a943464:132783e8:19cdff95 (local to host Microknoppix) Events : 0.4824680 Number Major Minor RaidDevice State 0 8 2 0 active sync /dev/sda2 1 8 17 1 active sync /dev/sdb1 2 8 33 2 active sync /dev/sdc1 3 8 49 3 active sync /dev/sdd1 However, there is no trace of the volume groups. Rebooting into knoppix does not help Restarting the old system (I actually replugged and re-added the failing disk for that – the system begins to start, but then fails to see the / partition – no wonder if the volume group is gone) does not help. sudo vgscan, sudo vgdisplay, sudo lvs, sudo lvdisplay, sudo vgscan –mknodes all returned No volume groups found. I am completely at a loss. Can anyone tell me if and how I can recover my data? Thanks in advance!