My software RAID is all screwed up

Question

I just discovered that my software RAID, which I set up as a RAID-1, is now showing up as a degraded array with a spare. I dropped and re-added the disk that it thinks is "spare", but it's still a spare. How do I make that spare into the mirror?

xen64:/# mdadm --detail /dev/md0
/dev/md0:
        Version : 00.90
  Creation Time : Mon May  3 20:56:55 2010
     Raid Level : raid1
     Array Size : 973828096 (928.71 GiB 997.20 GB)
  Used Dev Size : 973828096 (928.71 GiB 997.20 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sun Nov  7 08:18:50 2010
          State : active, degraded, recovering
 Active Devices : 1
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 1

 Rebuild Status : 3% complete

           UUID : 796cb574:f1263d29:de01a688:bcce49e1
         Events : 0.1279509

    Number   Major   Minor   RaidDevice State
       0       8        3        0      active sync   /dev/sda3
       2       8       19        1      spare rebuilding   /dev/sdb3

Answer 1

you raid is already rebuilding. "Rebuild Status : 3% complete"

the spare disk is marked "spare rebuilding", so when the rebuild has completed you disk will be marked "active sync"

nothing to do here

edit:
by the way, you can already start using the raid, even if it is degraded or still recovering, but heavy disk usage will ofc slow down the recovery process