File:LUG2019-LNet Feature Overview-Shehata.pdf

In this talk we will go over the major LNet features which have been developed for the community releases of Lustre over the past few years. The presentation aims to be user centric. It will cover the main functionality provided by Multi-Rail, Dynamic Discovery, LNet Health, Multi-Rail Routing and User Defined Selection Policies. It will give configuration examples of how all these features can be configured on the system to get maximum performance, reliability and control.

Multi-Rail feature brought the ability to utilize multiple interfaces over the same network. LNet can also use multiple networks to communicate with peers. Performance testing has shown that Multi-Rail almost aggregates the bandwidth of the interfaces. With Dual EDR cards LNet selftest has shown read/write bandwidth of approximately 24 GB/s.

Dynamic Discovery simplifies Multi-Rail configuration by dynamically discovering peer interfaces without having to explicitly configure them, as will be shown in this presentation.

LNet Health came on the heels of Multi-Rail and brought reliability and redundancy to LNet. With Health, LNet can monitor the errors on the links and dynamically switch to a healthier interface if one is available without dropping messages.

As the LNet design have become more Multi-Rail oriented, it became clear that the routing code needed to be brought inline with LNet’s Multi-Rail design. This was done in order to benefit from the performance and reliability aspects of Multi-Rail and Health. The presentation will cover the configuration changes introduced by the Multi-Rail Routing feature.

Finally, with multiple paths available for traffic to take, many use cases have been discovered that will benefit from the ability to control which interfaces message should be sent to and from. The User Defined Selection Policies (UDSP) feature brings the ability to configure policies to do just that. By the end of the presentation it should be clear how all these features work together, the benefit they bring to a Lustre installation, and how they can be configured to work smoothly.