CAUTION Please ensure you have additional backup of your data prior to continuing the recovery

On Ubuntu Linux I have RAID-1 set up for various data backups. One day when I attempted to boot to Ubuntu I failed to do so. After some preliminary troubleshooting it was found that most of RAID-1 array members could not be mounted. When inspected further the mdadm tool, a tool used to create RAID-1 array, showed that superblocks for affected RAID array members were missing.

The following page describes in detail how to recover a RAID array in similar circumstances: Irreversible mdadm failure recovery The command that resolved this particular problem was:

mdadm --create /dev/md/vol<RAID array member #> --level=1 --chunk=512K --metadata=1.2  --data-offset=262144s   --raid-devices=2 /dev/sd<disk 1 of RAID-1> /dev/sd<disk 2 of RAID-1> --assume-clean --readonly

Notes:

• As a result the RAID partitions have been mounted in read-only mode which is at least sufficient to ensure data is intact.
• One suspicion about what could cause such the error is that after the latest update the Ubuntu fsck was erroneously run against RAID array. To ensure fsck is not run against RAID array the Pass column in the /etc/fstab configuration file needs to be set to 0 as follows.

# Device                Mountpoint              FStype          Options Dump Pass
UUID of disk      mountpoint            ext4             rw              0       0