Problem with raidhotremove

[Martin Lichtin]

Anyone know why raidhotremove does not work?

[root]# raidhotremove /dev/md0 /dev/sdb1
/dev/md0: can not hot-remove disk: disk busy!

This is on a boiler-plate RH 6.2 system.

I _think_ I could use the "failed-disk" feature and 
run mkraid --force, but I'm not sure, so I better don't...