Alessandro Perilli noted our recent change to the number of supported virtual machines per core for Intel Nehalem (Xeon 5500 series) CPUs. In case you’re wondering, we support up to 16 VMs per core on XenServer today, for XenDesktop workloads.

The new support level is based on exhaustive testing with the Project VRC 2.0 workload for virtual desktops. Bernie Hannon, who has conducted our experiments, has discovered some interesting comparative results for XenServer versus other hypervisors too. You can read about his testing here.

Suffice it to say that XenServer 5.5 is the hands-down leader in performance for hosted virtual desktops. This remains true even in the presence of memory overbooking and common code page sharing, neither of which helps to increase the maximum number of useable VMs per server. Because comparative results require careful testing and even permission from other vendors before they can be published, we have simply elected to raise our own support levels, and to note that our competitor has not yet managed to do the same.

If you are interested in this topic, you should plan to come to Citrix Synergy in San Francisco, in May, where we plan to demonstrate the scalability of Citrix XenDesktop 4, and show what’s coming on the technology roadmap as we drive towards being able to scalably and affordably deliver tens of thousands of virtual desktops.