A few questions from customer, which I am unable to answer (might be easy for you experts):
1. Can I retain my data for two years?
2. What shall be data retention and overwriting policy?
3. What data shall be kept in DB? (logs, Traps, Notifications, etc)?
4. What shall be database growth rate?
5. Database Sizing?
It's pretty much impossible to answer this question with any input.
It's likelly that your disk space is going to be driven by NTA, which now (in NTA 4.0) has a dedicated database to store flow data (it's not in the Orion SQL database). You can find more about NTA database sizing here.
As far as theSQL Server database, which wil be impacted mostly by NPM, you can find our generic recomm and best practices here