I rarely work with storage systems - I'm a software guy. But on occasion I need to manipulate storage arrays for either performance tuning, or new installations. IBM has a new product group of storage called their "D-series", which is geared toward mid-sized businesses and they've put out a training site to help customers get started with external storage arrays. Its a very well put together flash-based site and I learned a good bit about storage basics I did not already know.
Direct Attach Storage, I know about, but SANS were a black art until I read this.