mdadm --assemble --scan

mdadm: /dev/md/diaghost05102010:2 has been started with 2 drives.
mdadm: /dev/md/diaghost05102010:1 has been started with 2 drives.
mdadm: /dev/md/diaghost05102010:0 has been started with 2 drives.
-bash-3.1# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid6] [raid5] [raid4] [multipath]
md125 : active raid1 sda1[0] sdb1[1]
      14658185 blocks super 1.2 [2/2] [UU]
     
md126 : active raid1 sda2[0] sdb2[1]
      58604024 blocks super 1.2 [2/2] [UU]
     
md127 : active raid1 sda3[0] sdb3[1]
      1880246440 blocks super 1.2 [2/2] [UU]
      [>....................]  resync =  0.0% (1228928/1880246440) finish=407.7min speed=76808K/sec
     
unused devices: <none>

The only strange thing is that the drives were all renamed to something high, md125,126 and 127 when I originally created them as 0,1,2

What if you don't want to assemble the array?

You can just scan like this

mdadm -D -s

ARRAY /dev/md/diaghost05102010:2 metadata=1.2 name=diaghost05102010:2 UUID=d851091d:3d109a17:921ab0e1:3a465899
ARRAY /dev/md/diaghost05102010:1 metadata=1.2 name=diaghost05102010:1 UUID=f841529d:a434b994:6f27c55b:64f4ef7d
ARRAY /dev/md/diaghost05102010:0 metadata=1.2 name=diaghost05102010:0 UUID=cba74a1f:e1c83abe:1ea30dc3:cee425bd

To see the details of a specific array just do this:

mdadm -D /dev/md/diaghost05102010:2
/dev/md/diaghost05102010:2:
        Version : 1.2
  Creation Time : Mon May 10 22:05:48 2010
     Raid Level : raid1
     Array Size : 1880246440 (1793.14 GiB 1925.37 GB)
  Used Dev Size : 1880246440 (1793.14 GiB 1925.37 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Wed May 12 23:37:54 2010
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           Name : diaghost05102010:2
           UUID : d851091d:3d109a17:921ab0e1:3a465899
         Events : 6

    Number   Major   Minor   RaidDevice State
       0       8        3        0      active sync   /dev/sda3
       1       8       19        1      active sync   /dev/sdb3