If you are designing a multi-TB database and do not understand all the design issues you need to pay to outside help. Period.

When processing a database of this size, a 2% difference in performance can result in extra hours of processing. Unless you really know how to fine tune your design to get the last 1% or 2% out of it, you almost certainly will end up with something that is either very slow or is using a few $100k more kit than it needs.

IMHO you should build a business case for your employer to engage an external consultant to help you with these issues. There are a number of high-reputation organisations in the market that can do this work, but if you are really stuck for names ask your Microsoft Account Manager for advice.