Maximum server memory
Generally in our setup guide, I recommend that you leave 4GB or 10% free for the operating system, whichever is larger. In this case, 4GB is larger, so you'd set max server memory to 28000.

The free memory is for:


Other services like SSIS, SSAS, SSRS (and if you use those extensively, you'll want to leave more memory aside)
Remote desktopping in (I wish people didn't, but so many folks RDP in and run SSMS or other tools)
Systems management apps (Dell OpenManage, HP SIM, etc that fire up and gobble memory)
Backup tools


If you monitor the Perfmon counter for Available Memory over time, and you consistently notice that most of the memory is going unused, then you can inch up max server memory to a higher number.