System optimization and tuning is tricky business. Benchmarking such systems is even more complicated as the number of things which can go wrong at doubles at the least. FreeBSD is best known for its killer features, but it also includes over 2500 sysctls, most of which can be tuned to do something interesting. This talk aims to give an overview of some of the more interesting things which can be tuned in FreeBSD, and advice on how to avoid the most common errors in benchmarking FreeBSD. Tuning a system heavily depends on hardware present in the system, so all tuning advice will necessary contain system-specific parts, but overall there is much to discuss when talking about optimizing specific systems: networking, storage, file systems, even the CPU scheduler. Networking is still very much dependant on the quality of the NIC and its driver, but large parts of the systems such as ZFS are pure software and can benefit from tweaks and tuning which slightly alter the behaviour of algorithms. Things get very complicated when comparing different hardware configurations, and even more when comparing different operating systems. Doing a good benchmark of two unrelated operating systems is tricky because it requires similar tune-ups to both systems. This talk will try to explain where the pitfalls are, and also present some field results.