There are a couple of different technologies that can be used to interconnect the elements of of a SAN. Another consideration is the SAN software, and again there are a couple of different styles to think about.
First the hardware. I can think of three existing technologies, 2 lighting fast, but complex and expensive. The other is simpler, but doesn't carry as much data.
Fibre channel uses optical links to connect the elements of your system. Each workstation will need an interface card, and you will need a special switch to connect them to. The drive arrays must also be designed to work with a fiber channel interface. As sort of side note to this CalDigit has an interesting optical system that does not use Fibre Channel, but rather a propriatary method of extending and switching the PCIe buss. The big advantage here is speed. If you work with uncompressed material or do a lot of multi cam work, this could be the way to go.
The alternative is to look at systems that use gig-E ethernet connections. These are simpler to install, require less specialized hardware, and therefore can be had for somewhat smaller budgets. These work quite well for any workflow that consists of compressed source and master material. Even the Avid Isis system uses this type of architecture and for many folks this is an ideal way to go.
One of the biggest issues with a SAN is controlling file permissions. If you just plug your computers and disks together you can in fact access the material just fine. However, if two systems try and write the the same file at the same time the wheels come off the bus. Not only will it muss that file, but will play merry hell with the rest of the volume. I saw this happen once and it was really not pretty. So this leads to needing a software solution to control file access. The software that does this falls into two basic categories. volume locking and file locking.
In volume locking each editor is assigned exclusive rights to write to a volume. Anyone can read files on the system, but only one person can write to any specific volume. In file locking systems it appears that everyone can read and write to anything as the software changes permissions on the fly for each file as write requests come in.
Often this control is handled by a server that you must install as part of your SAN build. I know of at least one product that will let you use one of your workstations to administer the SAN. There are then issues of how to deal with the problem of that workstation dropping offline.
While it is possible to build and configure one of these systems yourself if you are tech savvy, I would strongly recommend that you hire some help, or purchase a configured system for your first attempt. After all, with your whole business running on a single system, having issues with your SAN will be mighty ugly.
-Vance
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