This tip was excerpted from the book "Domino System Administration", by Rob Kirkland, New Riders publishing. New Riders.
If you're still in the process of rolling out Domino, or you are still planning to do so, one of the most difficult issues you face is how much server power you need. Central to that question is the subsidiary question of how much disk space you need. If you're already running Domino, you may have found that you need more disk space. But how much?
Simple answer: All you can get. But that flies in the face of real-world considerations, such as budgets and other trivia.
It is perhaps not so easy to predict how much disk capacity you will need. Lotus says you need 270MB just to install Domino and recommends 1GB total free disk space for program and data. But that's really just for starters. For anything more than a test platform, you will sooner or later need more disk space than that. Also, you will want more than one physical disk drive.
A rule of thumb that I have heard for mail servers (which are by far the biggest disk hogs among Domino servers) is to provide 50MB per mail user. It seems as though, no matter how hard you try (and Domino gives you the tools), you'll never be able to control some users' penchants for saving everything forever.
For other types of servers, you can consult with the designers of the applications that the servers will be hosting to determine what those applications' disk needs will be. If the designers are not available or are otherwise not helpful, you can run tests on the applications themselves to determine how much disk space various kinds of documents will occupy, then estimate the numbers of documents that are likely to accumulate. Rather than try to predict your ultimate disk capacity needs, you may prefer to configure your servers with disk hardware that is easily expandable.
For more information on Domino System Information, or to buy this book, click here.