Creating btrfs subvolume like @ or @home

Creating btrfs subvolume like @ or @home

Being intrigued by btrfs I decided to toy around with it in a VM.
Installation works great as long as I remember to put /boot on a separate
partition and it all seems to work fine.
What I would like to do is create a separate subvolume for bulk data with
different settings than things like @ and @home. btrfs subvolume create
data will do that for me, but I'm curious why it keeps naming it @/data
(or similar things when I try /data or @data). Is there a special way to
create the subvolumes like @ and @home so my data subvolume will show up
as @data? (and: what is the exact difference between the naming schemes?)



Additional information:
ubuntu 12.04.2, running as a KVM guest on mint15 host;
kernel 3.8.0-27-generic from ubuntu-x-swat (raring backport);
btrfs using two devices, /dev/sda and /dev/sdb
/dev/sda and /dev/sdb are partitions on a disk not used by the host OS