The memory required for SharePoint Server 2010 is directly related to the size of the content databases that you are hosting on a server that is running SQL Server.
As you add service applications and features, your requirements are likely to increase. The following table gives guidelines for the amount of memory we recommend.
Combined size of content databases
Minimum for small production deployments
Minimum for medium production deployments
Recommendation for up to 2 terabytes
Recommendation for the range of 2 terabytes to a maximum of 5 terabytes
Microsoft definitions of small and medium deployments are those described in the "Reference Architectures" section of the article Capacity management and sizing for SharePoint Server 2010.
These values are higher than those recommended as the minimum values for SQL Server because of the distribution of data required for a SharePoint Server 2010 environment. For more information about SQL Server system requirements, see Hardware and Software Requirements for Installing SQL Server 2008 (http://go.microsoft.com/fwlink/?LinkId=129377).
Other factors that may influence the memory required include the following:
- The use of SQL Server mirroring.
- The frequent use of files larger than 15 megabytes (MB).
For more information please download the whitepaper from Microsoft site :