Hard Disk Reference

There was a reference to a site about the hard disk a few days ago in the oracle-l list from Ranko Mosic. I have gone through half of it for now, I can say the referenced pages are a great guide for understanding the basics of the hard disk, its parts, inner workings, etc... Trying to tune I/O without knowing about the hard disk basics can lead a DBA to the wrong path easily, this site is a must read in my opinion.