Specifications

Best Practices for Virtualizing and Managing Exchange 2013

SLAT technologies also help to reduce CPU and memory overhead, thereby allowing more virtual

machines to be run concurrently on a single Hyper-V machine. The Intel SLAT technology is known as

Extended Page Tables (EPT); the AMD SLAT technology is known as Rapid Virtualization Indexing (RVI),

formerly Nested Paging Tables (NPT).

Best Practices and Recommendations

For optimal performance of demanding workloads like Exchange 2013, run Windows Server 2012

Hyper-V on SLAT-capable processors/hardware. This offers the additional benefits of improved

performance, greater virtual machine density per host machine, and reduced overhead as

compared to non-SLAT systems.

Virtual Processors

A virtual processor or a virtual CPU (vCPU) is a representation of the physical core of a processor or the

threads/logical processors in the core. A virtual machine is configured with at least one vCPU that

represents time on the physical CPU resource stack. Hyper-V supports configuring virtual machines with

more than one virtual processor from multiple physical or logical processors. In other words, one virtual

machine can be configured to use multiple physical processor cores at the same time, and this can

increase performance in many cases. Such virtual machines are called Symmetric Multi-Processing (SMP)

virtual machines. With SMP functionality, applications can benefit from multi-threading while running

virtual machines on Hyper-V, thereby enabling workload performance to be optimally distributed as long

as enough cores are available. This can be achieved by monitoring the CPU workload on the host.

As previously discussed, Windows Server 2012 Hyper-V supports virtual machines with up to 64 virtual

processors and 1TB memory. With increased support for 320 logical processors on a host machine, Hyper-

V in Windows Server 2012 can now support up to 2,048 virtual processors per host.

Note

Unlike the earlier version of Windows Server, there is no VP:LP ratio imposed by Hyper-V in

Windows Server 2012. However, Exchange 2013 supports a VP:LP ratio of no greater than

2:1—and a ratio of 1:1 is recommended.

Windows Server 2012 Hyper-V also provides the Weights and Reserves feature (Figure 3). Weights are

assigned to a virtual processor to grant it a larger or smaller share of CPU cycles than the average cycle

share. Reserves are set for a virtual processor to ensure that it gets at least a specified percentage of the

total possible CPU usage of a virtual machine when there is contention for CPU resources. Simply put, if

there is higher demand for CPU than is physically available, Hyper-V ensures that a virtual machine

needing CPU resources gets at least its CPU reserve when there is contention.

This feature is especially

beneficial for system administrators who want to prioritize specific virtual machines depending on the

load they have or need to handle.