My Raid 5 array (4 1tb Disks WD10EARS) had was showing as degraded. I looked and one of the disks wasnt installed, so i re-added it with the mdadm add command. the array is now showing as (null)Array , but cant be mounted if i run: root@warren-P5K-E:/home/warren# sudo mdadm --misc --detail /dev/md0 I get: mdadm: cannot open /dev/md0: No such file or directory and running: root@warren-P5K-E:/home/warren# cat /proc/mdstat gives me: Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] unused devices: < none > The data is very important root@warren-P5K-E:/home/warren# mdadm --examine /dev/sda /dev/sda: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b792 - correct Events : 1 Number Major Minor RaidDevice State this 1 8 0 1 spare /dev/sda 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# mdadm --examine /dev/sdb /dev/sdb: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7a0 - correct Events : 1 Number Major Minor RaidDevice State this 0 8 16 0 spare /dev/sdb 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# oot@warren-P5K-E:/home/warren# mdadm --examine /dev/sdc /dev/sdc: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7b4 - correct Events : 1 Number Major Minor RaidDevice State this 2 8 32 2 spare /dev/sdc 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# mdadm --examine /dev/sdd /dev/sdd: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7c6 - correct Events : 1 Number Major Minor RaidDevice State this 3 8 48 3 spare /dev/sdd 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd That on the 4 drives.