The plan we have is to have both BES servers using same SRP pointing at the shared SQL Database, although one server would have its services disabled and would only be enabled if the live server failed.
This is the correct DR scenario to have in place
Another option we had was to use two live servers with different SRP's although I heard moving large amounts of users from server to server is an issue? ALso Im guessing another server SRP costs extra money?
2 live BES will cost you the price of another BES. For 325 users one BES is plenty.
I would be really interested to hear your opinions on how you think we should proceed to carry out the software upgrade, migration to SQL and introduce another server for DR capabilities?
Step 1 should be to move the DB fro MSDE to the SQL Server. Use this article: BlackBerry Search Results
Once the 4.0 BES is working with the DB on the SQL Server upgrade to 4.1. The install the DR BES and make sure that both BES names are the same. The phyical machine name doesn't matter but the name in the BlackBerry Manager must be the same on both BES.
The keep the services stopped and set to manual until you need to use them.