Recently I got a question about in what cases should you split site collection and content databases in a 'site/portal/your configuration here'. The question came up after reading my post about MOSS limitations. Although it's very hard to get to those limitations, it could be the case that would like to create 2000 sub sites... right?
Anyway, the choice of splitting it into different content databases, and therefor also different site collections, depends on other things as well. If you won’t expect to exceed 2000 sub sites, it wouldn’t be a reason to split up. But there are some other things to take into consideration:
- The integration level – if you split, you cannot use content query web parts to query all the collections. The site collections are separated in content and security with the advantages, or disadvantages, that come with it.
- Security – splitting site collections is easier to control when it comes to security. Of course it is no problem to secure different sub sites, lists or list items, but the chance of mistakes is always a risk. Different site collections are much more controllable and easier to maintain when it comes to security.
- Storage – if you are intending to use huge amounts of data in a collection you can use different databases to be more flexible. It's easier to migrate databases or to control the load of the SQL server.
- Site collection quota's. Its easier to manage and control site collections with quota's.
- Backup and restore. In most cases we see that if it comes to a portal divided into departments, one site collection is used. When also using WSS sites for projects/communities etc, in the same interface, it might be a good idea to split those into other content databases.
Basically, there are no hard guidelines in which cases you should split up or not, but it's always good to plan before you try. So, also check out the planning section for MOSS on TechNet.