This evening I was asked whether I would recommand disabling IIS log file to make sure the SMP console runs as fast as possible.
My answer was (and remains) a big NO. Do _not_ disable IIS logging. It contains a lot of good information on it (that I am a big consumer of, but the value is there to anyone).
So, first lets dispell this nonsense about improving performances.
IIS logging is done on the http.sys driver, so it run in the Windows Kernel. You can verify this using procexp as per the image below. This means logging requests once they are completed (as this is when it) does not cost any context switching (as it would if it was in living user space). Besides, each entry is normal less than 1024 bytes, which means the "cost" of logging entries is fractional: push the information already held in memory to disk.
If you compare the cost of doing this tiny little task with what happens in user mode in the w3wp.exe (handling the request in ISAPI...