We are actually in the middle of setting up a hosting service actually. We have redundant server, switches, power, hard drives, etc. I am quite impressed with the MD3000i actually. We use it to hold our databases and virtual machines. We have it mostly set up now, just getting some marketing stuff ready and finalizing software, networking etc.
As for the SAN barrier, You could build a relatively cheap SAN with a low powered server, 3 or 4 1Tb hard drives, and a copy of freenas, openfiler, or pretty much any linux os that can run iscsi-target. You might have not be able to run as much IO through it as a dedicated SAN, but the failover would still be there and would still perform quite well