We at VMware have been fielding a lot of inquiries lately from customers who have virtualized (or are considering virtualizing) their Microsoft Lync Server infrastructure on the VMware vSphere platform. The nature of inquiries is centered on certain generalized statements contained in the “Planning a Lync Server 2013 Deployment on Virtual Servers” whitepaper published by the Microsoft Lync Server Product Group. In the referenced document, the writers made the following assertions:
- You should disable hyper-threading on all hosts.
- Disable non-uniform memory access (NUMA) spanning on the hypervisor, as this can reduce guest performance.
- Virtualization also introduces a new layer of configuration and optimization techniques for each guest that must be determined and tested for Lync Server. Many virtualization techniques that can lead to consolidation and optimization for other applications cannot be used with Lync Server. Shared resource techniques, including processor oversubscription, memory over-commitment, and I/O virtualization, cannot be used because of their negative impact on Lync scale and call quality.
- Virtual machine portability—the capability to move a virtual machine guest server from one physical host to another—breaks the inherent availability functionality in Lync Server pools. Moving a guest server while operating is not supported in Lync Server 2013. Lync Server 2013 has a rich set of application-specific failover techniques, including data replication within a pool and between pools. Virtual machine-based failover techniques break these application-specific failover capabilities.
VMware has contacted the writers of this document and requested corrections to (or clarification of) the statements because they do not, to our knowledge, convey known facts and they reflect a fundamental misunderstanding of vSphere features and capabilities. While we await further information from the writers of the referenced document, it has become necessary for us at VMware to publicly provide a direct clarification to our customers who have expressed confusion at the statements above. Continue reading