snapshot on 6.8.5/FC development

Hello,

I just tried the lvm2/dm-snapshot feature and failed miserably... After reading some older postings in this and the dm-devel mailing lists I'm not sure what to do:

setup:
lvm2-2.0.21
kernel-2.6.8
xfs

VG-Size: 4G on Raid-Mirror (/dev/md1)
LV-Size: 1G

Calling:

lvcreate --snapshot --size 100m --name snap /dev/TestMirrorGroup/OnlineVol

will block forever. I have to reboot the computer. After that /dev/TestMirrorGroup/snap is there...

I froze xfs before (xfs_freeze -f)

Any Clue? Is this related to xfs-FS only or do there exist general problems (I read somewhere about problems snapshotting raids...)

BTW: Why isn't it possible to create the snapshot on another VG than the original. This would be quite nice becauce in a typical setup it could be an advantate to have the snapshot on a small extra disk, keeping the original data separated from the writes to the snapshot.

Any help appreciated,

-Gunnar