It turns out that RHEL 5 Xen conversions don't work if the source disk
is located on a block device. See patch 1/4 for the gory details.
This patch series proposes a new tool called virt-v2v-copy-to-local
which essentially is a way to make new virt-v2v work like the old
virt-v2v, ie. copy first, convert after. Of course this is very slow
and would only be used as a last resort, but I identified two
situations in which this would currently be useful (see explanation in
patch 4/4).
This is also available in my git repo:
https://github.com/rwmjones/libguestfs/commits/master
Rich.