[vox-tech] Setting up raid, SET_ARRAY_INFO failed for /dev/md0: File exists

[vox-tech@lists.lugod.org]

Hi again (my problems are running fast and furious).  I just installed
Sarge, upgraded the kernel to 2.4.26 (using the kernel-image-2.4.26-1-k7,
cause I'm on AMD).  When I try to create my first software raid device I
get:

platinum:~# mdadm -C /dev/md0 --level raid1 --raid-disks 2 missing /dev/hdc1
mdadm: SET_ARRAY_INFO failed for /dev/md0: File exists

I try it on md1 instead:

platinum:~# mdadm -C /dev/md1 --level raid1 --raid-disks 2 missing /dev/hdc1
mdadm: SET_ARRAY_INFO failed for /dev/md1: File exists

try it on md3

platinum:~# mdadm -C /dev/md3 --level raid1 --raid-disks 2 missing /dev/hdc1
mdadm: array /dev/md3 started.

It starts.  I haven't created any md(s) before this, how can they exist?
How do I remove them?

How do I remove hdc1 from the md?  I tried:
platinum:/dev# mdadm --remove /dev/md3 /dev/hdc1
mdadm: hot remove failed for /dev/hdc1: Device or resource busy

Thanks
Jay