== Xen versus VMware for me

I've recently spent some time thinking about virtualization technology,
in particular how I feel about Xen versus VMware. In theory the choice
should be a slamdunk for me, because VMware requires evil binary kernel
modules and I have usually avoided that sort of thing even when it was
somewhat painful (eg, I don't use ATI's binary X drivers). In practice,
though, I am only distantly lukewarm on Xen and much more interested in
VMware.

The simple summary why this is is that Xen is a commitment, but VMware
is a flirtation.

I call VMware a flirtation because it will run on an otherwise ordinary
system (provided that I have enough kernel source around to compile its
modules). Installing and using VMware is thus a reasonably casual thing,
something I can do without particularly perturbing the system. I can
even normally boot my system with VMware's kernel modules loaded, and
only contaminate things if I actually need it this time around.

Xen's hypervisor approach requires a much bigger change in my system; I
can't add Xen to a running system, I have to boot the Xen environment
from the start. Which requires a special Xen-enabled kernel, which
requires special patches that you have to integrate into your kernel,
which [[gives me nervous flashbacks NPTLScars]]. Being able to run stock
kernels is valuable for me, and with Xen I give that up, so setting
things up for Xen means a fairly significant commitment.

(If Xen ran on top of a stock kernel.org kernel, I would be much more
interested, because it would be much less of a commitment.)

There are also additional reasons for my tilt towards VMware. First,
VMware has a more polished environment right now, with a GUI and various
convenient bits and all. Second, VMware's approach is much more useful
for what I do with virtualization than Xen's is, because VMware is
oriented towards running unmodified guest OSes in a complete virtual PC
environment.

The Xen hypervisor approach is I think clearly the right way of doing
things like running services in isolated virtual machines. But I'm not
doing that; instead I'm using virtualization for testing, where I really
want to run the exact same kernel and environment that I will wind up
running on the real hardware. (And thus it is a definite feature that
VMware emulates a complete PC, hokey BIOS booting and all.)