Question
Do you have a recommendation for the maximum number of databases you can place on a single SQL Server? I understand the memory and drive size requirements are big factors, but is there a maximum recommended number of actual databases you should place on a single SQL Server instance on a single server?
Answer
The total number of databases on a particular server is not all that relevant. What is important is how busy each of the databases are (and to a certain degree, the size of the databases in relation to the size of the available disk space). I have servers with only one very busy database, and other servers with many, many databases (all very little used).
So what you really must consider is the total overall load on each physical SQL Server, not the total number of databases on each server (unless database size is an issue). Performance Monitor can be used to help you determine if a particular SQL Server currently is experiencing bottlenecks or not. If you will be setting up one or more new SQL Servers, determining how many databases should be on each server is not an easy task as you probably don’t know what the load on each database will be. In this case, you will have to make educated guesses on database usage in order to best distribute databases among multiple SQL Servers to get the biggest performance benefits. And once you get some experience with the databases in production, then you can then move them around as appropriate to balance the load.
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