Long running hosts at the moment, but we can drain most workloads off a specific host/rack if required and reschedule it pretty fast. We have the advantage of having a custom scheduler/orchestrator we've been working on for years, so we have a lot of control on that layer than with Kube or Nomad.
Re: Live Migration We're working on adding Live Migration support to our orchestrator atm. We aim to have it running this quarter. That'll makes things super seamless.
Re: kernels We've already seen some perf improvements somewhere between 6.0 and 6.5 (I forget the exact reason/version) - but it was some fix specific to the Sapphire Rapids cpus we had. But I wish we had more time to science on it, it's really fun playing with all the knobs and benchmarking stuff. Some of the telemetry on the new CPUs is also crazy - there's stuff like Intel PCM that can pull super fine-grained telemetry direct from the CPU/chipset https://github.com/intel/pcm. Only used it to confirm that we got NUMA affinity right so far - nothing crazy.