For the purposes of determining the amount of memory required for the computers running SQL Server 2005, first determine whether the planned deployment is small, medium, or large in terms of memory consumption.
Determine your deployment size by using the following table:
If your deployment parameters are generally less than the listed values, your deployment can be considered small.
If your deployment parameters are approximately equivalent to the listed values, your deployment can be considered medium.
If your deployment parameters are generally greater than the upper limits of most of the listed values, your deployment can be considered large.
Content database size
50 GB
Number of content databases
20
Number of concurrent requests to SQL Server 2005
200
Users
1000
Number of items in regularly accessed list
2000
Number of columns in regularly accessed list
For SQL Server 2005, 4 gigabytes (GB) is the minimum required memory, 8 GB is recommended for medium size deployments, and 16 GB and greater above is recommended for large deployments.
Other factors that can influence your memory needs include:
The use of SQL Server 2005 mirroring.
The frequent use of files larger than 15 megabytes (MB).
Para más información: http://technet.microsoft.com/en-us/library/cc298578.aspx, http://technet.microsoft.com/en-us/library/cc298801.aspx