I am setting up a ESXi 4.0 server and have decided to use the CD installers ability to install to a USB key. I have a freebie slow 1GB Newegg USB key and a very fast 4GB Patriot Xporter XT Boost USB key. I'd like to use the Patriot somewhere else, but if speed makes a difference, I'll just buy another one.
Does the speed of the USB key make a noticeable difference when running ESXi?
I have no concrete benchmarks, but from trying it, the answer is only when initially loading the hypervisor.
I used a 8GB Very Fast USB stick, but then I needed to use it for something else so I replaced it with a cheap 2GB one that I got for free at a trade show.
It boots slightly slower when actually starting ESXi, but once it is loaded and at the half yellow/grey screen, I can not see any difference in speed at all.
I think ESXi will load and run in memory, so once it's loaded it'll run fine. I don't know if you'd need swap but I assume that would be on one of the datastores, not the USB drive.
I don't know if you'd want it to be anywhere but datastores and memory anyway because it would wear on the USB drive if it kept having to access it all the time.