>>Debian as the host OS.
Ah, the choices are almost boundless ("Linux is about choice") 
Tar is probably as good a way as any. I do this with a (36.5GB)Vista VM running on openSUSE:
simple tar:
Command prompt from the directory where my VM is located:
tar -cjvf /data250/testvs2008 .
(uses normal compression, probably gzip would be faster)
That creates a tarball (named testvs2008) of everything in the current directory, and puts it in the directoy /data250
It gave me several "status" messages such as:
tar: ./Windows Vista VS2008-2-s005.vmdk: file changed as we read it
tar: ./Windows Vista VS2008-1-s004.vmdk: file changed as we read it
tar: ./Windows Vista VS2008-1-s002.vmdk: file changed as we read it
Linux uses the honor system (and permissions) to protect open files....
It takes over an hour, I think, but it creates a 14.5GB tarball, out of a 36.5GB directory, full of my Vista machine (with VS2008) files. Eliminating compression would speed things up. If you don't need to do a chron job with it, you could just use konqueror or some such to copy the files. I like to compress to copy to my laptop or USB drive.
I then, do a:
tar -xjvf /data250/testvs2008
from the directory where I wanted to create the copy of the VM.
It uncompresses all 36.5 GB and I can start the VM (after deleting all the .lck files/directories). It asks me if I moved or copied and I always tell it moved so as not to aggravate Vista by changing the MAC. When I booted Vista in the VM, it acted as if it had had an abnormal shutdown, probably because it thought I had kicked its feet out from under it. Whether this would disturb a server VM, I can't answer, haven't tried it but I would think not. What I would probably do if this was a production VM is use the ntbackup or some other backup program in the VM to save the systemstate which should also backup the PDC, you are probably doing this anyway along with any DB program (they usually can recover from the journal). I have never had it lose anything but it is a "point in time" backup anyway. We backup our systemstate at least once a week. If our domain was more critical or large, I would do it daily.
rsync is another good backup program, that is what I use on our file server (also openSUSE), it allows an update mode, only copying newer files and can sync by deleting anything on the target that is not on the source. If you want to make an image, you can use dd or ddrescue (handles bad sectors) but I try to keep things simple. I think it was Alfred Einstein who said something like: You should keep things simple, but no simpler than necessary.
Lou
"In the beginning there was nothing, and God said: 'Let there be light'. And there was still nothing .. but now you could see it."
