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Checking Linux RAID array status

Wed, 01/13/2010 - 18:20 — Sean

This website runs on a pair of drives in a RAID-1 configuration, as do several pairs of drives in my home that I use for storing media (music, movies, television, etc.). On all servers, I run software raid in Linux using mdadm. For some reason, I can never remember the simple syntax for checking the status of an array:

$ sudo /sbin/mdadm -QD /dev/md0
/dev/md0:
        Version : 00.90.03
  Creation Time : Fri Jun 19 06:16:37 2009
     Raid Level : raid1
     Array Size : 104320 (101.89 MiB 106.82 MB)
  Used Dev Size : 104320 (101.89 MiB 106.82 MB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0
    Persistence : Superblock is persistent
 
    Update Time : Wed Sep 16 00:22:58 2009
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
 
           UUID : b185a678:1789acb9:327678ee:0f02177d
         Events : 0.14
 
    Number   Major   Minor   RaidDevice State
       0       3        1        0      active sync   /dev/hda1
       1       3       65        1      active sync   /dev/hdb1

The State line and Working Devices are the most important for me. In this case, they indicate the array is just fine and both drives are working.