I just made the switch in the lab now before calling it a week. I'm testing backups to the SAN over the weekend so I should have some results on Monday.
Is it just XO that uses https by default when talking xapi or do pool members default to https as well when talking with each other? If it makes as much as a difference as is expected here, wouldn't http by default be the answer for xcp-ng with the option to turn on ssl if needed? Assuming xcpng hosts are connected to well protected management and SAN networks only then http shouldn't be an issue.
Maybe run it on both http and https and let the admin decide which interfaces to bind to which ports based on need during install or at least via config file changes?
If hosts are talking https by default, can they be switched to http using something similar to this? It just seems like the perf gains are pretty significant and if you're running your pool on a secured management network then this seems like a potential big win for perf.