I thought the UUID stuff was a red herring. Here's the output from 2.6.20-12, where everything works ok: $ sudo dmraid -ay -vvvv -dddd WARN: locking /var/lock/dmraid/.lock NOTICE: /dev/sda: asr discovering NOTICE: /dev/sda: ddf1 discovering NOTICE: /dev/sda: hpt37x discovering NOTICE: /dev/sda: hpt45x discovering NOTICE: /dev/sda: isw discovering NOTICE: /dev/sda: jmicron discovering NOTICE: /dev/sda: lsi discovering NOTICE: /dev/sda: nvidia discovering NOTICE: /dev/sda: nvidia metadata discovered NOTICE: /dev/sda: pdc discovering NOTICE: /dev/sda: sil discovering NOTICE: /dev/sda: via discovering NOTICE: /dev/sdb: asr discovering NOTICE: /dev/sdb: ddf1 discovering NOTICE: /dev/sdb: hpt37x discovering NOTICE: /dev/sdb: hpt45x discovering NOTICE: /dev/sdb: isw discovering NOTICE: /dev/sdb: jmicron discovering NOTICE: /dev/sdb: lsi discovering NOTICE: /dev/sdb: nvidia discovering NOTICE: /dev/sdb: nvidia metadata discovered NOTICE: /dev/sdb: pdc discovering NOTICE: /dev/sdb: sil discovering NOTICE: /dev/sdb: via discovering NOTICE: /dev/sdc: asr discovering NOTICE: /dev/sdc: ddf1 discovering NOTICE: /dev/sdc: hpt37x discovering NOTICE: /dev/sdc: hpt45x discovering NOTICE: /dev/sdc: isw discovering NOTICE: /dev/sdc: jmicron discovering NOTICE: /dev/sdc: lsi discovering NOTICE: /dev/sdc: nvidia discovering NOTICE: /dev/sdc: pdc discovering NOTICE: /dev/sdc: sil discovering NOTICE: /dev/sdc: via discovering DEBUG: _find_set: searching nvidia_acihdbbb DEBUG: _find_set: not found nvidia_acihdbbb DEBUG: _find_set: searching nvidia_acihdbbb DEBUG: _find_set: not found nvidia_acihdbbb NOTICE: added /dev/sda to RAID set "nvidia_acihdbbb" DEBUG: _find_set: searching nvidia_acihdbbb DEBUG: _find_set: found nvidia_acihdbbb DEBUG: _find_set: searching nvidia_acihdbbb DEBUG: _find_set: found nvidia_acihdbbb NOTICE: added /dev/sdb to RAID set "nvidia_acihdbbb" DEBUG: checking nvidia device "/dev/sda" DEBUG: checking nvidia device "/dev/sdb" DEBUG: set status of set "nvidia_acihdbbb" to 16 INFO: Activating mirror RAID set "nvidia_acihdbbb" NOTICE: discovering partitions on "nvidia_acihdbbb" NOTICE: /dev/mapper/nvidia_acihdbbb: dos discovering NOTICE: /dev/mapper/nvidia_acihdbbb: dos metadata discovered DEBUG: _find_set: searching nvidia_acihdbbb1 DEBUG: _find_set: not found nvidia_acihdbbb1 DEBUG: _find_set: searching nvidia_acihdbbb2 DEBUG: _find_set: not found nvidia_acihdbbb2 DEBUG: _find_set: searching nvidia_acihdbbb3 DEBUG: _find_set: not found nvidia_acihdbbb3 NOTICE: created partitioned RAID set(s) for /dev/mapper/nvidia_acihdbbb INFO: Activating partition RAID set "nvidia_acihdbbb1" INFO: Activating partition RAID set "nvidia_acihdbbb2" INFO: Activating partition RAID set "nvidia_acihdbbb3" WARN: unlocking /var/lock/dmraid/.lock DEBUG: freeing devices of RAID set "nvidia_acihdbbb" DEBUG: freeing device "nvidia_acihdbbb", path "/dev/sda" DEBUG: freeing device "nvidia_acihdbbb", path "/dev/sdb" DEBUG: freeing devices of RAID set "nvidia_acihdbbb1" DEBUG: freeing device "nvidia_acihdbbb1", path "/dev/mapper/nvidia_acihdbbb" DEBUG: freeing devices of RAID set "nvidia_acihdbbb2" DEBUG: freeing device "nvidia_acihdbbb2", path "/dev/mapper/nvidia_acihdbbb" DEBUG: freeing devices of RAID set "nvidia_acihdbbb3" DEBUG: freeing device "nvidia_acihdbbb3", path "/dev/mapper/nvidia_acihdbbb" $ ls -l /dev/mapper/ total 0 crw-rw---- 1 root root 10, 63 2008-05-01 17:57 control brw-rw---- 1 root disk 253, 0 2008-05-01 22:50 nvidia_acihdbbb brw-rw---- 1 root disk 253, 1 2008-05-01 22:50 nvidia_acihdbbb1 brw-rw---- 1 root disk 253, 2 2008-05-01 22:50 nvidia_acihdbbb2 brw-rw---- 1 root disk 253, 3 2008-05-01 22:50 nvidia_acihdbbb3 (no errors from dmesg) and from 2.6.24-16: $ sudo dmraid -ay -dddd -vvvv WARN: locking /var/lock/dmraid/.lock NOTICE: /dev/sdc: asr discovering NOTICE: /dev/sdc: ddf1 discovering NOTICE: /dev/sdc: hpt37x discovering NOTICE: /dev/sdc: hpt45x discovering NOTICE: /dev/sdc: isw discovering NOTICE: /dev/sdc: jmicron discovering NOTICE: /dev/sdc: lsi discovering NOTICE: /dev/sdc: nvidia discovering NOTICE: /dev/sdc: pdc discovering NOTICE: /dev/sdc: sil discovering NOTICE: /dev/sdc: via discovering NOTICE: /dev/sdb: asr discovering NOTICE: /dev/sdb: ddf1 discovering NOTICE: /dev/sdb: hpt37x discovering NOTICE: /dev/sdb: hpt45x discovering NOTICE: /dev/sdb: isw discovering NOTICE: /dev/sdb: jmicron discovering NOTICE: /dev/sdb: lsi discovering NOTICE: /dev/sdb: nvidia discovering NOTICE: /dev/sdb: nvidia metadata discovered NOTICE: /dev/sdb: pdc discovering NOTICE: /dev/sdb: sil discovering NOTICE: /dev/sdb: via discovering NOTICE: /dev/sda: asr discovering NOTICE: /dev/sda: ddf1 discovering NOTICE: /dev/sda: hpt37x discovering NOTICE: /dev/sda: hpt45x discovering NOTICE: /dev/sda: isw discovering NOTICE: /dev/sda: jmicron discovering NOTICE: /dev/sda: lsi discovering NOTICE: /dev/sda: nvidia discovering NOTICE: /dev/sda: nvidia metadata discovered NOTICE: /dev/sda: pdc discovering NOTICE: /dev/sda: sil discovering NOTICE: /dev/sda: via discovering DEBUG: _find_set: searching nvidia_acihdbbb DEBUG: _find_set: not found nvidia_acihdbbb DEBUG: _find_set: searching nvidia_acihdbbb DEBUG: _find_set: not found nvidia_acihdbbb NOTICE: added /dev/sdb to RAID set "nvidia_acihdbbb" DEBUG: _find_set: searching nvidia_acihdbbb DEBUG: _find_set: found nvidia_acihdbbb DEBUG: _find_set: searching nvidia_acihdbbb DEBUG: _find_set: found nvidia_acihdbbb NOTICE: added /dev/sda to RAID set "nvidia_acihdbbb" DEBUG: checking nvidia device "/dev/sda" DEBUG: checking nvidia device "/dev/sdb" DEBUG: set status of set "nvidia_acihdbbb" to 16 WARN: unlocking /var/lock/dmraid/.lock DEBUG: freeing devices of RAID set "nvidia_acihdbbb" DEBUG: freeing device "nvidia_acihdbbb", path "/dev/sda" DEBUG: freeing device "nvidia_acihdbbb", path "/dev/sdb" dmesg: [ 322.015422] device-mapper: table: 253:0: mirror: Device lookup failure [ 322.015428] device-mapper: ioctl: error adding target to table $ ls -l /dev/mapper total 0 crw-rw---- 1 root root 10, 63 2008-05-01 22:58 control