Windows 2012 RSS & DVMQ

Receive-Side Scaling (RSS) plays an important role in Microsoft’s Windows Server 2012 strategy, enabling something called SMB Multichannel on high-capacity NICs.

When packets arrive in a NIC to be processed, the NIC has always relied on a single core in the processor. As servers and their workloads have grown, this single-core solution has become a bottleneck.

RSS is a feature in the network card (using queues) and driver that allows a supporting operating system, such as Windows Server 2012, to dynamically scale up/down the processing of incoming traffic for no virtualized workloads across multiple cores. RSS is for no virtualized workloads.

RSS enables SMB Multichannel on high-capacity NICs, enabling file services to fully utilize bandwidth for application workloads.

Important for Hyper-V:

  • Faster Cluster Shared Volume (CSV) redirected I/O
  • Support for storing Windows Server 2012 Hyper-V virtual machines on Windows Server 2012 file servers

Dynamic Virtual Machine Queuing (DVMQ)
DVMQ does for virtualization traffic passing through a virtual switch what RSS does for networking traffic for no virtualization workloads. Virtual NIC traffic is processed by more than one core, enabling much greater performance and scalability.

Planning for DVMQ
DVMQ uses the same queues on the NIC. Those queues can be either dedicated to RSS or dedicated to DVMQ, but not both. Therefore, a NIC or a NIC team is configured for either RSS or DVMQ.

All of the requirements settings, calculations, and configurations for DVMQ are the same as they are for RSS.

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