Re: [Xen-users] Xen alternatives

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I have worked with Xen, VMware ESX and qemu. Since you need to run
> Windows and VT technology is not widely available yet, your choices are
> reduced to full virtualization via VMware or qemu. VMware ESX is costly
> but well supported. It is actually based on Red Hat 7.x. It has good SAN
> support, training, add ons like VMTN and Virtual Center add up a pretty
> solid product that you can use for a corporate or institutional
> environment. Performance is not as good as Xen but probably on par or
> better then qemu (haven't tried the qemu-accelerator myself).

I'd expect VMware to still perform better (for kernel / IO intensive stuff, 
particularly) than Qemu at this stage, although Qemu is a very impressive 
piece of software and is rapidly developing.

VMware will also use SMP fully.  Qemu now supports SMP guests but IIRC it 
doesn't support SMP hosts: i.e. all a guests' processors are multiplexed on 
one host CPU so it's just a testing tool, rather than a means of improving 
CPU bandwtich.  VMware ESX does up to 4 virtual CPUs per guest IIRC; I'm not 
sure about GSX.

> qemu on the other hand is mostly open source,

Worth noting that the accelerator is currently closed source, if that matters 
to anyone.  It's still free-as-in-beer though.  Mmmm free beer.

> supports a wider variety 
> of (emulated) platforms, runs on more platforms (e.g. FreeBSD and
> Windows versions are available) and also "supports" more platforms
> although it has a more limited scope of peripheral emulation (sound
> cards and such). qemu is better for labs and skunkworks-type projects,
> non-profits & startups with tiny budgets, and of course tinkerers and
> hackers.

There are also plenty of cool patches floating around to add features to Qemu 
- several are incorporated in the Qemu device model used by Xen/VT-x.

Depending on how important Windows is to you, running Xen on the host and Qemu 
or Win4Lin Pro (which is Qemu based - Win4Lin explicitly support running 
Windows on Xen as a configuration) in guests may be worth looking at.  You 
don't need special hardware, and will be able to live-migrate Windows guests.  
Windows won't run so fast, but Linux guests will obviously be very good 
performance.  Just depends what's more important!

Cheers,
Mark

> That's all the spew I have time for now, but good luck in your decision.
> HTH.

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