For a long time VMware was pretty much the only option for running Virtual machines on Linux and Windows. But this year, there seems to be a lot of alternatives. Parallels has been around for a year or two now, VirtualBox seemed to appear at the start of this year, Xen (or XenSource … or however you’re meant to refer to it these days) is really start to get into full swing with commerical offerings from Xensource, as well the SUSE VirtualIron and the Xen built into Redhat 5 (and possibly other linux distros). Then you have the QEMU type VMs; qemu itself with its accelerator, Win4lin Pro (which I think is based on qemu), plus more recently we have linux’s built in
KVM.

I haven’t tried all of them. I’ve tried VMware Server and Workstation on linux, Parallels on linux, VirtualBox on linux, Xen on Centos 5 (which is essentially Redhat 5) and KVM. With respect to running Windows on these platforms I still think VMware does a very good job. VirtualBox could easily give them a run for their money. its quite a well thought out product … very similar to VMware workstation, and it just gives a sense of ‘smoothness’ that is generally something you give up with VMs as you never seem to have enough memory or CPU power. It’s also mostly free. Parallels is also OK. It costs money. Given that the likes of Vmware Server and VirtualBox are free, it’s a hard sell.

Centos 5 Xen seems promising, but my experience installing XP on it was rather dismal. I’ve used linux VM’s running on a Xen host and they do run rather well. I am guessing that linux VMs paravirtualised on Xen run quite impressively but Windows VMs on Xen are a bit average. Xensource seems quite serious at competing with VMware ESX, so it’ll be interesting to see how that goes.

I should try Win4lin Pro. Many years ago I did try the older Win4lin for Windows 9x. It was very impressive speedwise. But all I’ve heard are bad reviews regarding the speed of the Win4lin Pro product.