Get ready for a massive change in the coming years. Many know Single Root I/O Virtualization or SR-IOV. The new standard is emerging as Scalable IO Virtualization. Originally this was donated as an Intel specification, but it is now part of OCP. The main goal of Scalable IOV is to provide performance paths to access hardware while that hardware is shared in an increasingly virtualized, containerize, and composable infrastructure.
Scalable IO Virtualization is Replacing SR-IOV
These days, SR-IOV is well supported, but it is not perfect. SR-IOV was designed originally for 20 or so VMs. The vast majority of cloud instances are 8 vCPUs or less. As we move to 60-128 cores/ 120-256 threads in 2023, and then into several hundred cores per socket going forward, each CPU in a dual socket server will easily eclipse that 20 VM mark. Beyond that, new devices and topologies with things like CXL mean that the industry needs a different solution. That solution seems like it is going to be Scalable IO Virtualization or Scalable IOV.
The main benefits that OCP members, like Microsoft are touting are scalability, flexibility, over-provisioning, and compatibility. For those wondering, SR-IOV can still be supported with backward compatibility in a Scalable IOV system.
Scalable IOV uses hardware-assisted, efficient routing and has different modes for direct path and intercepted path functions. The intercepted path can be handled in software or on an embedded controller. While allowing more fine-grained, and performance and access.
If you want some holiday reading material, checking out the OCP Scalable I/O Virtualization spec would be a great way to learn more. At STH, we will cover Scalable IOV as we start to see it more in future generations of servers.
Since it is Christmas Eve and I am on my second-to-last flight of 2022, I just wanted to share some of my holiday reading material that I have had bookmarked since it was presented at the OCP Summit 2022 Keynote a few months ago. Tomorrow we will have our Q4 Letter from the Editor, but I wanted to get a quick piece up and say Merry Christmas to the STH community.