It is possible to synchronise a volume to an other node in a defined interval.
So if a node fail there will be an copy of the volumes from a VM
on an other node.
With this copy it is possible to start the VM on this node.
this adds the functions for listing the disks (mostly copied from
the ceph code), checking if a disk is a valid blockdevice, if it
is used/in a zfs pool/as an lvm pv, and an init function (just to add a gpt header;
this is important if one wants to use a fresh disk for ceph journals)
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
