[Qemu-devel] Re: What can qemu do that vmware/virtual pc can't...article idea

[Don Kitchen]

I've heard that VMware has the ability to do delta (incremental) images but
I've never found it. With Qemu it's easy to make a large (read-only) system
image (burned to CD or DVD, for example) and have all disk writes go to
a different smaller media (like the USB flash drive you booted from, which
is how qemu on knoppix on a PC with one DVD drive can have access to
a 7GB compressed system image without using the hard disk.

Also disk image deltas can be useful to have small variations on a base
system. For example, an incremental image whose only change is to set some
application option, another incremental image whose only change is to set
a different option, or perhaps a new incremental image for every new
windows patch that comes out. Need to test something against win2k with only
critical patches applied? Or all patches until a particular one? That would
all be possible, and all of it sharing and reusing a common disk image,
instead of having 20, 50, or 100 full duplicates of a system install.

Unfortunately it's difficult to change the location of a base image once
incremental images are made, and bridged ethernet funcationality could be
a problem for some uses, but overall qemu is very versatile.