mdadm

root@bf:~# mdadm --examine /dev/sda1
/dev/sda1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : c56473fe:a12dd859:d52b8dae:15c027ef
           Name : bf:0  (local to host bf)
  Creation Time : Sun Jan 30 20:09:48 2011
     Raid Level : raid1
   Raid Devices : 2

 Avail Dev Size : 968744960 (461.93 GiB 496.00 GB)
     Array Size : 968744688 (461.93 GiB 496.00 GB)
  Used Dev Size : 968744688 (461.93 GiB 496.00 GB)
    Data Offset : 2048 sectors
   Super Offset : 8 sectors
          State : clean
    Device UUID : f8e14efa:91bae3bd:979ad96a:15f8e824

    Update Time : Tue Jul 17 05:37:36 2012
       Checksum : 282c5918 - correct
         Events : 825398


   Device Role : Active device 0
   Array State : A. ('A' == active, '.' == missing)

root@bf:~# mdadm --examine /dev/sdb1
/dev/sdb1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x2
     Array UUID : c56473fe:a12dd859:d52b8dae:15c027ef
           Name : bf:0  (local to host bf)
  Creation Time : Sun Jan 30 20:09:48 2011
     Raid Level : raid1
   Raid Devices : 2

 Avail Dev Size : 968744960 (461.93 GiB 496.00 GB)
     Array Size : 968744688 (461.93 GiB 496.00 GB)
  Used Dev Size : 968744688 (461.93 GiB 496.00 GB)
    Data Offset : 2048 sectors
   Super Offset : 8 sectors
Recovery Offset : 121093120 sectors
          State : active
    Device UUID : 9b0b0742:11465b34:37066a66:f7f8d9b1

    Update Time : Mon Jul 16 21:09:44 2012
       Checksum : 76139726 - correct
         Events : 815009


   Device Role : Active device 1
   Array State : AA ('A' == active, '.' == missing)
root@bf:~#

root@bf:~# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Sun Jan 30 20:09:48 2011
     Raid Level : raid1
     Array Size : 484372344 (461.93 GiB 496.00 GB)
  Used Dev Size : 484372344 (461.93 GiB 496.00 GB)root@bf:~# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Sun Jan 30 20:09:48 2011
     Raid Level : raid1
     Array Size : 484372344 (461.93 GiB 496.00 GB)
  Used Dev Size : 484372344 (461.93 GiB 496.00 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Tue Jul 17 05:41:00 2012
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 1
  Spare Devices : 0

           Name : bf:0  (local to host bf)
           UUID : c56473fe:a12dd859:d52b8dae:15c027ef
         Events : 825592

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

       2       8       17        -      faulty spare   /dev/sdb1
root@bf:~#

   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Tue Jul 17 05:41:00 2012
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 1
  Spare Devices : 0

           Name : bf:0  (local to host bf)
           UUID : c56473fe:a12dd859:d52b8dae:15c027ef
         Events : 825592

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

       2       8       17        -      faulty spare   /dev/sdb1
root@bf:~#