These are some exciting times for the world of virtualization and there has been plenty of virtualization news today with LinuxWorld in full swing. Microsoft is now officially supporting Linux running inside of Microsoft Virtual Server. VMware has recently made their virtual machine player and basic server product free along with their Open Machine Virtual Disk Specification and their CEO Dianne Greene even issued an open challenge to Microsoft in her most recent blog. XenSource will soon be running unmodified versions of Windows and other operating systems on a routine basis once hardware virtualization support Intel and AMD becomes common later this year. XenSource is halting their management products while Virtual Iron is beefing up their's but adopting XenSource's virtual machine format.
At the heart of VMware's message is that the Virtual Machine file format should be license free and that Virtualization should not be tied to an operating system. But Microsoft's VHD format is also "royalty free" and has been adopted by XenSource and many other companies. As for OS independence, VMWare currently runs on top of Linux, FreeBSD, or Windows while Microsoft's virtualization product primarily runs on Windows. David Berlind also asked "should Linux host Windows or Windows host Linux" but if you ask XenSource they'll say neither and tell you to use their 50K line micro-kernel. While VMware has a high-end ESX server product that doesn't rely on any commodity operating system, it is still running a stripped down version of FreeBSD. While that's certainly better than Microsoft's offering, it's still no where close to the size of XenSource's tiny micro-kernel. What VMware does have going for them is their market lead and ease of use. Since VMware released their free Virtual Player, it has almost become the de facto standard for demonstration technology since anyone can post virtual images of complex environments that are ready to click and play. VMware's Appliance center is full of virtual images ready for download and community built images especially interesting.
XenSource's approach is very interesting since the virtual machine Hypervisor (host) has no uptime or security dependencies on any commodity operating system and it doesn't get any leaner than 50 thousand lines of code. XenSource CTO Simon Crosby described to me at last week's Vyatta party how small the Xen Hypervisor was and how Xen was able to transition a time-sensitive game server from one physical machine to another in less than 50 milliseconds without dropping a game client. The down side for XenSource is that recent studies have found that Xen is "hardly on the radar" for most customers while VMware was first and Microsoft a distant second. This could change rapidly once XenSource is capable of running any unmodified operating system and hardware virtualization is widely available on desktops, servers, and notebooks by the end of this year. Xen has already become closely integrated with Red Hat and SuSE Linux.