Specifications

Best Practices for Virtualizing and Managing Exchange 2013

Exchange 2013 Virtual Machine Network Considerations

Networking and network access are critical to the success of an Exchange deployment. Windows Server

2012 Hyper-V provides a number of capabilities, technologies, and features that an administrator can use

to drive the highest levels of networking performance for the virtualized Exchange infrastructure.

Legacy versus Synthetic Virtual Network Adapters

When creating a virtual machine, the administrator has two choices for virtual network adapters (or

vNICs): legacy or synthetic. A legacy adapter emulates an Intel 21140-based PCI Fast Ethernet Adapter,

which results in a lower data transfer than the network adapter. Legacy network adapters (also known as

emulated NIC drivers) should only be used when booting a virtual machine in the Pre-Boot Execution

Environment (PXE) or when installing guest operating systems that are not Hyper-V-aware.

Synthetic adapters are the preferred option for most virtual machine configurations because they use a

dedicated VMBus to communicate between the virtual NIC and the physical NIC. This results in reduced

CPU cycles, as well as much lower hypervisor/guest transitions per operation. The driver for the synthetic

adapter is included with the Integration Services that are installed with the Windows Server 2012 guest

operating system.

Best Practices and Recommendations

From an Exchange 2013 perspective, there is no reason to use the Legacy vNIC. At minimum,

customers should use the default synthetic vNIC to drive higher levels of performance. In addition,

should the physical network card support them, the administrator should take advantage of a

number of the NIC offloads that can further increase performance.

Single Root I/O Virtualization

The Single Root I/O Virtualization standard was introduced by the PCI-SIG, the special interest group that

owns and manages PCI specifications as open industry standards. SR-IOV helps to virtualize demanding

workloads like Exchange 2013 that require higher network and I/O performance. It does so by enabling

virtual machines to perform I/O directly to the physical network adapter by bypassing the root partition.

In Windows Server 2012, SR-IOV can be deployed in conjunction with key capabilities such as live

migration to enable high network performance with availability.

SR-IOV provides extensions to PCI Express (PCIe) devices like network adapters to separate access to its

resources among various PCIe hardware functions. Two of these functions are PCIe Physical Function (PF)

and PCIe Virtual Functions (VFs):

 PCIe Physical Function is the primary function of the device and advertises its SR-IOV

capabilities. The PF is associated with the Hyper-V parent partition in a virtualized environment.

 PCIe Virtual Functions are associated with the PF of the device. A VF shares one or more physical

resources, such as memory and network ports, with the PF and other VFs on the device. Each VF is

associated with a Hyper-V child partition in a virtualized environment.