Receive Side Scaling on UCS Blades

To implement enterprise application like SAP, Oracle or SQL on UCS virtualization environment. Default setting of UCS blades may not suitable for the application. We always expect highest performance by optimize hardware and ESXi. In my UCS training session, I noticed one "hidden" parameter may helpful for performance.

Receive Side Scaling – So called RSS, it's a feature that allows you to utilize multiple CPUs and multiple cores per CPU to process the receiving network load. Without RSS, all of the receive network traffic is processed by one CPU and by only one core of the CPU. Essentially, RSS distributes receiving network load to all of the CPUs and their cores.

The parameter is an option in BIOS, but it's not under BIOS policy in UCS Manager. You should go to Servers tab, extend Policies node, and check an Eth Adapter Policy under Adapter Policy node, Receive Side Scaling (RSS) is available in Options section of right frame. Blade should be rebooted to leverage the option.

Please keep in mind that do not enable RSS if your adapters more than your CPUs, it will cause unexpected network transmit failed. RSS option must be enabled on UCS policy before enable it on OS layer (I confirmed with Cisco TAC, is that true?). Regarding OS layer, please refer to those articles.

Receive side scaling on Intel® Network Adapters

How to enable Receive Side Scaling on Microsoft Windows Server 2008 R2

You don't have to enable the option if network traffic is not a concern.

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