> It's interesting that nobody so far mentioned openVZ or its commercial > version, Virtuozzo. It's different than all major virtualization players > (it's OS level virtualization, not hw level), but that makes it the only > viable option for things like mass web hosting solutions. > Try it out and see if it fits your requirements. The two things that always comes to mind when I am considering a virtualization solution is extent of tool set/support, and the general acceptance of the technology. For those two reasons I nearly always implement VMware, it has a mature set of tools, a wide range of functionality, and sits at a very manageable price point. No true open source solution really comes close, you can approximate parts of it, but in the end it turns into a support issue that can pose a significant headache.