VM can't use DRBD resource as harddisk?

Hi guys,

I have to copy VM to another host while it is running.
The VM disk image lays on LV in LVM group.
It has around 500GB so i can't afford the downtime while DRBD will sync the data over network. It would take few hours.

So here's what I did.

1. Pepared the configuration of the DRBD resource to use VM's LV disk image on node1 (created LV, and prepared config too on node2).
2. Stopped the VM.
3. Fired up DRBD resrouce and promoted it as primary so it could be writable.
4. Because you can't specify DRBD device in proxmox I started VM with DRBD resource using that long kvm command (... -drive file=/dev/drbd1,if=none,id=drive-virtio0,aio=native,cache=none ...).
Result: VM can't find/use that disk black screen on console.

Maybe the VM could use the LV directly but that could be very dangerous to data i think.
It should use DRBD resource insted.

The XEN hypervisor differs between used block devices with config syntax phy:/device/ and drbd:resource thereforce i think it has something to do with it.

Thanks for help