Any way to snapshot or otherwise backup a running vm?

[Petr Topiarz <topiarz%post.cz@localhost>]

Hi folks,

I use xen-project on NetBSD (host) and I look for a way to backup a 
running vm (various guests NetBSD, Linux, Windows).

What could work, but does not:
- Commercial Xen-Server is a closed stuff which will not work on NetBSD, 
so no "xe" commands for snapshotting
- LVM allows snapshotting, but this LVM feature is not implemented on NetBSD
- ZFS is ported to NetBSD but snapshotting is not in production quality

Can anyone help me find a way to backup a running virtual machine such 
as production webserver or DNS server on NetBSD's Xen?

Thank you
Peter