Since recently I was pretty sure that IIS and Apache are pretty much the same when it comes to performance.
I have never been so wrong!

I was naive but since I have always used Apache and the net is full of people that say IIS is very good it's understandable... and actually it's very used.

Recently I tested booting NimbleX 2008RC over HTTP and I had at hand the laptop of a friend of mine that uses WinXP so I clicked, clicked, clicked and I put the NimbleX ISO on his AMD dual-core laptop.

Soon I was booting NimbleX over the http protocol and I was pretty happy but wait. The CPU on the dual-core laptop jumped in ~50%. My first reaction was "This solution will never work!".

Just for the heck of it I copied the ISO to a 550MHz test server that has Linux & Apache and was at ~1.5Km (~1 mile) distance from me. Guess what? CPU usage was never more than 10%.

Conclusion! When I was accessing less than 50MB of random data at full speed from a 200MB file over HTTP the CPU usage was as follows:

IIS on WinXP and AMD X2 the CPU usage was ~50%
Apache on Linux and PII the CPU usage was ~10%

I'd like to think that this is a freak result but... I don't really think so.
I wonder why Google doesn't use IIS and Win?