I created a RAID with: sudo mdadm --create --verbose /dev/md1 --level=mirror --raid-devices=2 /dev/sdb1 /dev/sdc1 sudo mdadm --create --verbose /dev/md2 --level=mirror --raid-devices=2 /dev/sdb2 /dev/sdc2 sudo mdadm --detail --scan returns: ARRAY /dev/md1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb Which I appended it to /etc/mdadm/mdadm.conf, see below: # mdadm.conf # # Please refer to mdadm.conf(5) for information about this file. # # by default (built-in), scan all partitions (/proc/partitions) and all # containers for MD superblocks. alternatively, specify devices to scan, using # wildcards if desired. #DEVICE partitions containers # auto-create devices with Debian standard permissions CREATE owner=root group=disk mode=0660 auto=yes # automatically tag new arrays as belonging to the local system HOMEHOST <system> # instruct the monitoring daemon where to send mail alerts MAILADDR root # definitions of existing MD arrays # This file was auto-generated on Mon, 29 Oct 2012 16:06:12 -0500 # by mkconf $Id$ ARRAY /dev/md1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb cat /proc/mdstat returns: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md2 : active raid1 sdb2[0] sdc2[1] 208629632 blocks super 1.2 [2/2] [UU] md1 : active raid1 sdb1[0] sdc1[1] 767868736 blocks super 1.2 [2/2] [UU] unused devices: <none> ls -la /dev | grep md returns: brw-rw---- 1 root disk 9, 1 Oct 30 11:06 md1 brw-rw---- 1 root disk 9, 2 Oct 30 11:06 md2 So I think all is good and I reboot. After the reboot, /dev/md1 is now /dev/md126 and /dev/md2 is now /dev/md127????? sudo mdadm --detail --scan returns: ARRAY /dev/md/ion:1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md/ion:2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb cat /proc/mdstat returns: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md126 : active raid1 sdc2[1] sdb2[0] 208629632 blocks super 1.2 [2/2] [UU] md127 : active (auto-read-only) raid1 sdb1[0] sdc1[1] 767868736 blocks super 1.2 [2/2] [UU] unused devices: <none> ls -la /dev | grep md returns: drwxr-xr-x 2 root root 80 Oct 30 11:18 md brw-rw---- 1 root disk 9, 126 Oct 30 11:18 md126 brw-rw---- 1 root disk 9, 127 Oct 30 11:18 md127 All is not lost, I: sudo mdadm --stop /dev/md126 sudo mdadm --stop /dev/md127 sudo mdadm --assemble --verbose /dev/md1 /dev/sdb1 /dev/sdc1 sudo mdadm --assemble --verbose /dev/md2 /dev/sdb2 /dev/sdc2 and verify everything: sudo mdadm --detail --scan returns: ARRAY /dev/md1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb cat /proc/mdstat returns: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md2 : active raid1 sdb2[0] sdc2[1] 208629632 blocks super 1.2 [2/2] [UU] md1 : active raid1 sdb1[0] sdc1[1] 767868736 blocks super 1.2 [2/2] [UU] unused devices: <none> ls -la /dev | grep md returns: brw-rw---- 1 root disk 9, 1 Oct 30 11:26 md1 brw-rw---- 1 root disk 9, 2 Oct 30 11:26 md2 So once again, I think all is good and I reboot. Again, after the reboot, /dev/md1 is /dev/md126 and /dev/md2 is /dev/md127????? sudo mdadm --detail --scan returns: ARRAY /dev/md/ion:1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md/ion:2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb cat /proc/mdstat returns: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md126 : active raid1 sdc2[1] sdb2[0] 208629632 blocks super 1.2 [2/2] [UU] md127 : active (auto-read-only) raid1 sdb1[0] sdc1[1] 767868736 blocks super 1.2 [2/2] [UU] unused devices: <none> ls -la /dev | grep md returns: drwxr-xr-x 2 root root 80 Oct 30 11:42 md brw-rw---- 1 root disk 9, 126 Oct 30 11:42 md126 brw-rw---- 1 root disk 9, 127 Oct 30 11:42 md127 What am I missing here?