Raid 1, can't get the second disk added back in.

[Jim <jim@fayettedigital.com>]

Sometime in the distant past, I lost a member of my raid 1 group.  
Here's some output:

root@chinaberry:~# mdadm /dev/md0 --add /dev/hdb5
mdadm: Cannot open /dev/hdb5: Device or resource busy
root@chinaberry:~# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 hda5[1]
      93771264 blocks [2/1] [_U]

unused devices: <none>
root@chinaberry:~# cat /etc/mdadm.conf
DEVICE /dev/hdb5 /dev/hda5
ARRAY /dev/md0 level=raid1 num-devices=2

root@chinaberry:~# fdisk -l /dev/hdb

Disk /dev/hdb: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdb1               1         973     7815591   83  Linux
/dev/hdb2             974        1946     7815622+  83  Linux
/dev/hdb3            1947        2919     7815622+  83  Linux
/dev/hdb4            2920       14593    93771405    5  Extended
/dev/hdb5            2920       14593    93771373+  83  Linux
root@chinaberry:~# fdisk -l /dev/hda

Disk /dev/hda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hda1   *           1         973     7815591   83  Linux
/dev/hda2             974        1946     7815622+  83  Linux
/dev/hda3            1947        2919     7815622+  83  Linux
/dev/hda4            2920       14593    93771405    5  Extended
/dev/hda5            2920       14593    93771373+  83  Linux

I attempted to boot single user mode and fsck /dev/hdb5 but single user 
doesn't seem to do what it used to, for some reason /dev/md0 was 
mounted.  However I did boot Knoppix CD and do a fsck -f /dev/hdb5.  It 
had no errors and when I rebooted back it still wouldn't install.

I've searched the documentation and pretty much anything I try ends up 
with a "Cannot open /dev/hdb5: Device or resource busy" message.

Here's what mount says:
/dev/sda3 on / type ext3 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
/sys on /sys type sysfs (rw,noexec,nosuid,nodev)
varrun on /var/run type tmpfs (rw,noexec,nosuid,nodev,mode=0755)
varlock on /var/lock type tmpfs (rw,noexec,nosuid,nodev,mode=1777)
procbususb on /proc/bus/usb type usbfs (rw)
udev on /dev type tmpfs (rw,mode=0755)
devshm on /dev/shm type tmpfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda5 on /home type ext3 (rw)
/dev/md0 on /backupmirror type ext3 (rw)
/dev/hda1 on /vz type ext3 (rw)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)

from dmesg:
md: md0 stopped.
md: bind<hdb5>
md: bind<hda5>
md: kicking non-fresh hdb5 from array!
md: unbind<hdb5>
md: export_rdev(hdb5)
raid1: raid set md0 active with 1 out of 2 mirrors

And :
mdadm --detail /dev/md0
/dev/md0:
        Version : 00.90.03
  Creation Time : Fri Feb 23 15:03:40 2007
     Raid Level : raid1
     Array Size : 93771264 (89.43 GiB 96.02 GB)
    Device Size : 93771264 (89.43 GiB 96.02 GB)
   Raid Devices : 2
  Total Devices : 1
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sat Jan  5 10:45:47 2008
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           UUID : d01d66b4:16efa6c2:d7493088:59f3fe68
         Events : 0.28752

    Number   Major   Minor   RaidDevice State
       0       0        0        0      removed
       1       3        5        1      active sync   /dev/hda5

root@chinaberry:~# mdadm /dev/md0 --fail /dev/hdb5 --remove /dev/hdb5
mdadm: set device faulty failed for /dev/hdb5:  No such device
root@chinaberry:~# mdadm /dev/md0 --fail /dev/hdb5
mdadm: set device faulty failed for /dev/hdb5:  No such device

root@chinaberry:~# mdadm /dev/md0 --remove /dev/hdb5
mdadm: hot remove failed for /dev/hdb5: No such device or address
root@chinaberry:~# mdadm /dev/md0 --add /dev/hdb5
mdadm: Cannot open /dev/hdb5: Device or resource busy

All the solutions I've been able to google fail with the busy.  There is 
nothing that I can find that might be  using /dev/hdb5 except the raid 
device and it appears it's not either.

I'd be happy getting /dev/hdb5 back as a separate device and give up on 
raid entirely if that will solve this problem but I can't figure out how 
to get the raid drive to let loose of either partition.

Thanks for any guidance.  It worked for about 6 months then one day it 
went Poof!  I'm sure it was during a power failure.

Jim.