Planning an Xsan is perhaps the most complicated part of any deployment. First, start with one of two objectives, speed or size (or both). How big does the SAN need to be and what speeds does the SAN (aggregate speed of all clients) need to be able sustain? That becomes the primary design consideration. Beyond that, you’ll also want to plan how it will get backed up and when, the makeup of the clients (Mac, PC, Linux), how permissions will get handled for new files written to the SAN, etc.