2013
07.10

One for you SMB Multichannel freaks out there.  This KB article and hotfix from Microsoft is for when incorrect Receive Side Scaling (RSS) processor assignment on a Windows 8 or Windows Server 2012-based computer that has multi-core processors.

Symptoms

Consider the following scenario:

  • You have a Windows 8-based or Windows Server 2012-based computer that has multi-core processors.
  • You have three or more network adapters installed on the computer. 
  • You enable Receive Side Scaling (RSS) and set a RSS profile to use the "Closest" parameter for the network adapters.
  • You run the following PowerShell command to retrieve RSS properties of the network adapters:

Get-NetAdapterRss

In this scenario, the first two network adapters are assigned processors correctly. However, other network adapters are not assigned correctly.

Cause

This issue occurs because RSS incorrectly uses the maximum processor count that is supported by the computer to assign processors. The expected action is that RSS uses the active processor count during the processor assignment.

A supported hotfix is available from Microsoft.

There’s no mention of this applying if using DVMQ, the cousin of RSS.

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