When we perform diagnostics on an existing SQL Server instance, or if we are setting up a new machine, it’s very important to make sure that we change the Max Server Memory setting to an appropriate level.
If we don’t, then there’s a good chance (especially on Enterprise Edition) that SQL Server will use all the available memory on the server. Unfortunately, this means the operating system can be starved of RAM, which creates a performance bottleneck.
Additionally, other components (including other applications, services, and hardware on the machine) may have specific memory requirements, which need to be taken into account.
To get a baseline, I use a formula developed by Jonathan Kehayias (blog | twitter) which he wrote in his book, Troubleshooting SQL Server: A Guide for the Accidental DBA, and repeated in his blog post, “How much memory does my SQL Server actually need?”.
After many months of confusing myself with mental arithmetic, I decided to create a straightforward list based on Jonathan’s algorithm, in 4 GB increments, for my own reference. I would like to share this with you today.
Next time you (or I) need to check if the Max Server Memory setting is too high, simply open that link and check the matrix. Over time I will make it look prettier, but for now it is already helping one of my clients.
Let me know what you think on Twitter, with @bornsql.