It seems like an obvious question, but, how would you roll-out Enterprise Vault to 2000 users? You've done a nice, simple design. You've got the storage ready, and the server deployed. You've installed all the software, configured the policies that you've agreed on. But what then?
Well one way is to simply enable all 2000 users in one go.
Is that likely to work? Sometimes maybe, but not always. 2000 users will for sure come up with some questions, and more than likely inundate the company IT HelpDesk.
The solution is really down to communication, and that needs to start, ideally, before you get to the stage of throwing the big switch to turn on the system. Involving the end-users of the system, finding advocates that will help promoting the system, and of course, they might even help teach some of their colleagues how to use various aspects of it.
Once end-users are brought on board then I would suggest rolling out Enterprise Vault to some sizeable batches of people first of all, and gradually introducing more. Enterprise Vault helps with all of this by having provisioning groups. You could target particular OU's, or Active Directory groups. They're usually quite good ways to pick up some sizeable, common-interest groups. For example you could get all the sales and marketing people, or all the IT people, or all the marketing people.
Once you've done a few batches of people like this, with a few days at least between them, you can carry on and enable the remaining people group by group, and eventually just 'go for the rest', and enable all the remainder in one go. This final phase is dependent on the feedback that you get during the first few weeks, and the problems - aka Help Desk tickets - that get generated.