My workstation has two disks(/dev/sd[ab]), both with similar partitioning. /dev/sdb failed, and cat /proc/mdstat stopped showing the second sdb partition.

I ran mdadm --fail and mdadm --remove for all partitions from the failed disk on the arrays that use them, although all such commands failed with

mdadm: set device faulty failed for /dev/sdb2:  No such device
mdadm: hot remove failed for /dev/sdb2: No such device or address

Then I hot swapped the failed disk, partitioned the new disk and added the partitions to the respective arrays. All arrays got rebuilt properly except one, because in /dev/md2, the failed disk doesn't seem to have been removed from the array properly. Because of this, the new partition keeps getting added as a spare to the partition, and its status remains degraded.

Here's what mdadm --detail /dev/md2 shows:

[root@ldmohanr ~]# mdadm --detail /dev/md2
/dev/md2:
    Version : 1.1
  Creation Time : Tue Dec 27 22:55:14 2011
 Raid Level : raid1
 Array Size : 52427708 (50.00 GiB 53.69 GB)
  Used Dev Size : 52427708 (50.00 GiB 53.69 GB)
   Raid Devices : 2
  Total Devices : 2
Persistence : Superblock is persistent

  Intent Bitmap : Internal

Update Time : Fri Nov 23 14:59:56 2012
      State : active, degraded 
 Active Devices : 1
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 1

       Name : ldmohanr.net:2  (local to host ldmohanr.net)
       UUID : 4483f95d:e485207a:b43c9af2:c37c6df1
     Events : 5912611

Number   Major   Minor   RaidDevice State
   0       8        2        0      active sync   /dev/sda2
   1       0        0        1      removed

   2       8       18        -      spare   /dev/sdb2

To remove a disk, mdadm needs a device filename, which was /dev/sdb2 originally, but that no longer refers to device number 1. I need help with removing device number 1 with 'removed' status and making /dev/sdb2 active.