[fedora-virt] A really sparse disk image...

[Tom Horsley]

I had an ubuntu9.10 KVM using virtio to talk to a qcow2 image
file. One day I was trying to backup the file to a usb drive
with rsync -a -S and I could never get the checksums to match
(yes the virtual machine was shut down :-).

I then tried backing it up to a different name in the same directory
with the same result, no checksum match.

I then ran fsck on the drive (forcing it to check) - no problems
found :-).

Has anyone ever seen anything like this before? Can qcow2 map
disk pages to /dev/random? :-).

Eventually, I tried booting up one of the copies I made (which
could be backed up with good checksum matches), found that the
booted machine seemed to behave normally using the copy,
and just removed the funny image file that would never copy.