Towards the end of the XenServer 5.6 (“Midnight Ride”) release we added support for CPU masking features in modern Intel and AMD CPUs. This work was prioritized to help address the pain customers have reported in expanding their XenServer resource pools over time. Unfortunately, between finishing Midnight Ride, the long-pole work around our integration of Open vSwitch and Distributed Virtual Switching, and the push to get “Cowley” (XenServer 5.6 Feature Pack 1) into beta release it’s taken more time than we hoped to get the supporting collateral for the CPU masking features put together.

So I’m happy to post that we’ve published the first set of supported CPU combinations on the XenServer Hardware Compatibility List (HCL) and a Understanding Heterogeneous Pools in XenServer 5.6 Knowledge Base article that details how CPU masking support is implemented in XenServer, related changes to how CPUs are assessed for compatibility at pool join time, and how to determine compatibility of any particular set of CPUs.

Finally, because of the very large range of possible CPU combinations a key aspect to this support is that anyone can certify their own combinations using the new Heterogeneous Pools self-test kit. Once certified Citrix will add the combination to the HCL.

In XenServer 5.6 using the CPU masking features requires an Enterprise or Platinum license, but the related changes in how CPUs are assessed for compatibility will increase the number of CPUs that can be combined using the Free edition as well. Packaging decisions are still being finalized for the Cowley release.

XenServer host CPU requirements and the methods used to determine assess CPU compatibility has been a source of confusion in the past, so any feedback you have on these product changes and additional information is welcome.


Carl, on behalf of the XenServer engineering team