Check manual page of md

Linux softraid devices

Checks the current state of a Linux MD raid array. The information is read by the agent from /proc/mdstat. The result is either OK, if all disks are active or critical in any other case.

Item

The Linux raid device without /dev/, for example "md0".

Discovery

All RAID devices except those with raid level 0 are automatically detected. The RAID 0 devices's output is completely different from the others. And if a disk crashes you will soon notice anyway...