This is a good question because it is not easy to determine how far one should go with DR plans.
As a minimum, you have a responsibility to run frequent backups and store them away from your production site. Beyond this you need to explain to the business the various options, how they will work, and how much would they cost .. the business is to decide which one to pick.
Your main options are:
- Some sort of a reciprocal arrangement with a company that uses similar systems, so you use each other's site as your DR site. This way both companies get some from of a limited DR without additional hardware cost. The difficultly here is in pulling together some sort of an agreement and overcoming issues to do with security etc..
- Sign an agreement with a hosting service provider to use their hardware in case of a disaster. This is usually easy and involves little preparations.
- Build your own DR site which comes with a myriad of complexities and costs but when done well would be the ultimate solution.
But most importantly, you need to plan of action, what will everyone do in case of a disaster, who will recover the data, who will switch the users, are the users fully aware of the procedure .. etc..