(aka IOlwayscallsmethat. OK, horrendous joke based on a bad Dad Joke. Geneva has been notified.)
Exciting news over at the NTDebugging blog – a new Storport.sys update that enables ETW tracing of slow IO, for Windows 2008 and up.
It’s more involved than a registry-key-and-go, but if you’re facing what could be external delays on a SAN-connected box, it’s an excellent way of determining that (since it measures it essentially from the adapter on out).