Chad Sakac was recently touring APJ and delivering his high energy VMware+EMC message with demos, demos, and more demos. His encyclopedia-sized deck of technical gems included a short discussion on VMDirectPath that merits comment. I will offer my thoughts here.
Scott Drummonds on Virtualization
I heard a myth today that VMware did not support running vmxnet3 and PVSCSI in the same virtual machine. I have talked with a dozen engineers on the subject since it came up this morning and all swear the drivers run great together. The two drivers work on very different and unrelated stacks in the VMkernel. There are no inter-dependencies of any sort between PVSCSI and vmxnet3.
I think this rumor sprung from our somewhat limited support of paravirtualized drivers in FT-protected virtual machines, which will be improved in a subsequent release. And while most of you probably know that PVSCSI and vmxnet3 run together, I thought it worth a brief comment on this blog. Myths are like cockroaches. For every one you see there are hundreds hiding behind the walls.
You should probably not be reading this article.
What follows is my tale of performance optimizations so arcane and of extremely limited relevance as to make this guidance useful to one customer in 100,000. The parameters I reference here should rarely–if ever–be touched by a VI admin. I am documenting them for here for that one mischievous soul that is allowed to do as much damage as good in the pursuit of performance excellence. The rest of you should not even consider these changes for your production environment.
Seriously. Don’t do it. Don’t do it.