Running Lync Server on Virtual Servers

The following table shows the recommended base hardware for a host server.

Both the physical host servers and all virtual servers must run one of the following operating systems. Lync Server virtualization supports a mix of operating systems. For example, a host server running Windows Server 2012 that runs virtual servers that run Windows Server 2008 R2 is supported.

• Windows Server 2012. This is the recommended operation system for both host servers and virtual servers, to enable the best performance.
  
• Windows Server 2008 R2 with the software update described in Microsoft Knowledge Base article 981836, "Network connectivity for a Windows Server 2003-based Hyper-V virtual machine is lost temporarily in Windows Server 2008 R2," at http://go.microsoft.com/fwlink/p/?linkId=201212.
  

  Note:
  You must run this update on both the physical host server and all virtual machines, even though the Microsoft Knowledge Base article states otherwise.

You can mix physical and virtual servers in your deployment, with only the following restrictions:

• You cannot mix different types of servers within the same pool. All servers within the same pool must either be physical or virtual. For these purposes, Front End Servers and SQL Servers running the back-end database are considered to be separate, meaning that you can have virtual Front End Servers using a physical back-end database, or physical Front End Servers and a virtual back-end database. Note however that the back-end database has a real-time requirement for presence updates, which is unlike many SQL Server applications. If you run a virtual back-end database you must be aware of performance issues, especially if the host of the virtual back-end database is running other applications.
  This is the only limitation to mixing physical and virtual servers. You could have some Front End pools of physical servers and others of virtual servers. And you can deploy different types of pools and servers as either physical or virtual in any combination.
  
• All servers within one pool should provide about the same performance. For example, if you have virtual Front End Servers in one pool being hosted on different host servers, you should make sure each virtual Front End Server is capable of a similar level of performance.
  

If you are deploying a large amount of virtualized servers across different host servers, you should consider spreading out the members of one pool across different host servers. For example, in a pool of eight virtual Front End Servers, deploy four on one physical host and four on another. While this is not a true high-availability solution, it does provide some protection if a single host server fails.

Lync Server supports the use of virtual clustered storage. However, live migration (and other types of migration) of virtual servers running Lync Server is not supported. As with physical servers, Lync Server 2013 virtual servers do not support SQL clustering.

Lync Server provides real-time communications, and depends on fast and efficient networking. If a packet is delayed by as little as a few milliseconds, users might detect an audio glitch, experience a delayed call, or frozen video. To improve the network performance of your virtualized topology, you should do the following:

• The host must have at least one network adapter dedicated to the virtual machines running Lync Server roles. Sharing a network adapter with the host or with a storage area network (SAN) is not recommended.
  
• Note that a Lync Server workload that includes media can reach a peak network utilization of more than 500 Mbps.
  
• If one host server is running multiple guest virtual servers that each run Lync Server media workloads, ensure that the host network adapter can handle the traffic. To prevent bottlenecks, consider a higher speed network adapter (such as 10 GbE) or multiple network adapters using link aggregation.
  
• For best performance, use the Single Root I/O Virtualization (SR-IOV) capabilities of Windows Server 2012 Hyper-V. With SR-IOV, the virtual function of a physical network adapter is assigned directly to a virtual machine. This increases network throughput and reduces network latency while also reducing the host CPU overhead that is required for processing network traffic. To take advantage of SR-IOV, you must use a host server which has BIOS which supports SR-IOV, as well as use network adapters that support SR-IOV. Additionally, you must run Windows Server 2012 on both the host server and all virtual servers.
  
• Enable virtual LAN (VLAN) tagging on the network adapter, and implement multiple VLANs on the virtual servers to optimize network traffic.
  
• Implement multi-path I/O (MPIO) to your back-end database.
  

We recommend you use Microsoft System Center Virtual Machine Manager (VMM) to manage your virtualized Lync Server topology.

By using VMM, you do not need to use Terminal Services or Remote Desktop Services for the virtual machine management. Additionally, by using VMM you can view and manage performance, and other components such as disk space. You can also save a virtual machine as a template for creating new instances.

VMM uses Windows PowerShell, so you can create VMM Windows PowerShell scripts that integrate with Lync Server Management Shell to manage Lync Server.

For details about VMM, see the System Center Virtual Machine Manager website at http://go.microsoft.com/fwlink/p/?linkId=202887.