sudo mdadm -E /dev/sda1
/dev/sda1:
          Magic : a92b4efc
        Version : 00.90.00
           UUID : b4ccfd29:aa1e621b:966f9a8e:fb978859
  Creation Time : Sun Mar 25 23:51:03 2007
     Raid Level : raid1
    Device Size : 312568576 (298.09 GiB 320.07 GB)
     Array Size : 312568576 (298.09 GiB 320.07 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0

    Update Time : Mon Mar 26 11:12:20 2007
          State : active
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0
       Checksum : 4506f0ce - correct
         Events : 0.3


      Number   Major   Minor   RaidDevice State
this     0       8        1        0      active sync   /dev/sda1

   0     0       8        1        0      active sync   /dev/sda1
   1     1       8       17        1      active sync   /dev/sdb1