Great article on SAS : Serial Attached SCSI
by Derek Sivers
Great article explaining SAS (Serial Attached SCSI) here: http://www.tomshardware.com/2006/04/07/going_the_sas_storage_way/index.html
Don't do the usual Tom's Hardware thing where to click straight to the benchmarks and conclusion.
In this article, the first few pages are a great introduction to SAS and included some history about SATA and SCSI that I never knew as well.
Bookmark for when you have some quiet-time to read.