When Does Your System Need to Grow?http://www.websense.com/content/support/library/deployctr/v77/dic_ds_sys_grow.aspx
There are numerous triggers that might prompt your system expansion. Among them:
Performance issues
You may or may not be aware of performance issues affecting your system. If you are experiencing slow discovery or fingerprinting scans, for example, this could be an indication of an overworked crawler. You may benefit from an additional crawler or Data Security server. If user are experiencing slow Web or email transactions, you may benefit from an additional policy engine. Even if you are not aware of performance issues, your system resources may not be fully optimized. To see how your system is performing, open TRITON - Data Security and select Main > Status > System Health. You can expand each module and view statistics on the load, the number of transactions, the latency, and more. Before adding modules, try balancing the load between your existing Data Security servers (policy engines). To do this, go to Settings > Deployment > System Modules, and click the Load Balancing button. Select a service and indicate which policy engine you'd like to assign to that service.
Note: Websense recommends that you do not distribute the load to the TRITON Management Server.
The number of users grows
In a typical small organization (1–500 users), you might only need a TRITON Management Server and a protector to monitor traffic. A larger organization (500–2,500 users) might have a TRITON Management Server, a supplemental Data Security server, and a protector, with load balancing between the protector and supplemental server. (You cannot balance the load with the management server.) As your number of users grows, so does your need for a Data Security server.
Click View Complete Document for more.