Following steps involve moving some KVM VMs from file storage to block storage. 
This is basically converting the .qcow2 files to LVM LVs. It was surprisingly simple.
1. qemu-img convert disk0.qcow2 -O raw disk0.raw
2. ls -l
-rw-r—r— 1 user user 44023414784 2011-03-27 09:09 disk.raw
3. lvcreate -L 44023414784b -n lv_disk vgroup
4. dd if=disk.raw of=/dev/vgroup/lv_disk
dd if=/dev/vmlv/vm4992 of=/dev/vmlv/vm4992-new
qemu-img convert /dev/vmlv/vm4992 -O raw /dev/vmlv/vm4992
|  
 | 
| <disk type='file' device='disk'>  <driver name='qemu' type='qcow2' cache='none'/>  <source file='/srv/virtual/vm_web/tmp5GWO4q.qcow2'/>  <target dev='hda' bus='virtio'/></disk>   | 
| #Configuration After:  | 
| <disk type='block' device='disk'>  <driver name='qemu' type='raw' cache='none'/>  <source dev='/dev/vgroup/lv_disk'/>  <target dev='vda' bus='virtio'/></disk> |