You would like to design your infrastructure and need to know how many endpoint agents are supported per endpoint server.
There are no set limits of how many endpoints can be on an endpoint server.
According to the Symantec Data Loss Prevention Endpoint Server Scalability Guide testing is being performed with three host systems that each ran 10,000
simulated DLP Agents.
Number of agents supported with transient connection = 30,000
Number of agents supported with persistent connection = 10,000
However there are many things that will affect performance here are a few guides that will help you understand endpoint server performance.
About Endpoint Server redundancy
About discovering and preventing data loss on endpoints
Optimizing the scan for endpoint performance
Understand performance implications of enabling endpoint metadata detection
About Two-tier Detection for EDM on the Endpoint
Two-Tier Detection for DLP Agents
About policy creation for Endpoint Prevent
Guidelines for authoring Endpoint policies
Retaining data for endpoint incidents
Configuring the agent connection status
In summary:
The more data being retained, or two tier detection, and the more frequent your agent communications are the less agents each server can support.
Therefore a certain amount of server redundancy is recommended, you should monitor your communications periodically, and be prepared to scale up as your workload increases.