Update the CPU Estimates

Typically, you round up CPUs to an even number. Rounding up to an even number allows you to evenly split the CPU estimates between two physical servers and also adds a small factor for latent capacity. However, round up according to your specific needs for replication of services.

As a general rule, allow 2 gigabytes of memory for each CPU. The actual memory required depends on your specific usage and can be determined in testing.

The following table lists the final estimates for the identity-based communications example. These estimates do not include any additional computing power that could have been added for security and availability. Totals for security and availability will be added in following sections.

Table 5–4 CPU Estimate Adjustments for Supporting Components

Component	CPUs	Memory
Portal Server	4	8 GB
Communications Express	2	4 GB
Messaging Server(MTA, inbound)	2	4 GB
Messaging Server(MTA, outbound)	2	4 GB
Messaging Server(MMP)	2	4 GB
Messaging Server(Message Store)	2	4 GB
Access Manager	2	4 GB
Calendar Server	2	4 GB
Directory Server	4	8 GB (Rounded up from 3 CPUs/6 GB memory)
Web Server	0	0