I've admitted previously that I have a passion for characterization. When you really understand something you can be sure you are targetting the right problem, and the only way to do that with any certainty is data. Sometimes you've got to guess and make educated inferences, but way too many people guess when they should be measuring instead.
Val Henson highlights on lwn.net a couple great hard drive failure rate characterization studies presented at the USENIX File Systems and Storage Technology Conference. They cast doubt on a couple pieces of conventional wisdom: hard drive infant mortality rates, and the effect on ambient temperature on drive lifetime. This isn't gospel: every characterization study is about a particular frame of reference, but it is still very very interesting. Val Henson, as usual, does a fabulous job interpreting and showing us the most interesting stuff going on in the storage and file systems world.