making mirror

Hello
I've created btrfs on single partition (/dev/sdc3) using:
mkfs.btrfs /dev/sdc3
So far ... it is running fine - but i would like to switch to raid1 configuration. Unfortunately - i didn't pass any information about raid (-m raid1 -d raid1) when i created it :(

Now i would like to hot-add a /dev/sda3 (which is same size as currently used /dev/sdc3).
The problem is - that i don't have free space on other partitions - so i cannot move data away, create FS from start and copy data back to running mirror. Perfect solution would be a hot-adding new partition - but can i do it with btrfs-vol? If so - how?

regards,

manio
jabber/e-mail: [email protected]
http://manio.skyboo.net