- What data will need to be accessed and/or backed-up?
- How much storage is necessary?
- How many users will need access?
- Transfer speeds, especially if applications and other data will be accessed directly from the remote disk drives.
- Where will the remote drives be located? In the same building, offsite, etc.
- What is your budget?
Of course, each situation is different, but these are a good starting point for your plan.