I guess 1st thing is 1st, you will need to know what is the size of each calls and that is when you plan and cater for your SAN or NAS storage..
AS for encryption I believe you can directly encrypt the whole hdd directly..
if you have a vendor doing this for you, check out with the vendor what solutions he have for you
If you are using an EMC SAN it supports encryption as the data is written using their PowerPath MPIO driver stack. I talk about it in chapter 2 of my book “<a href=”http://www.amazon.com/Securing-SQL-Server-Protecting-Attackers/dp/1597496251/ref=sr_1_1?ie=UTF8&qid=1299906568&sr=8-1″>Securing SQL Server</a>”.