image).
This is equivalent to the qemu parameter
-C<-drive file=filename,cache=off,if=virtio>.
+C<-drive file=filename,cache=off,if=...>.
Note that this call checks for the existence of C<filename>. This
stops you from specifying other types of drive which are supported
changes to be committed, although qemu can support this.
This is equivalent to the qemu parameter
-C<-drive file=filename,snapshot=on,if=virtio>.
+C<-drive file=filename,snapshot=on,if=...>.
Note that this call checks for the existence of C<filename>. This
stops you from specifying other types of drive which are supported