• Disk IOPS
• CPU
• Active Directory CPU cores required to support Exchange users
• RAM for Mailbox, CAS, and multi-role server (Mbx+CAS)
A note from Microsoft on the minimum requirements for RAM:
Regardless of whether you are considering a multi-role or a split-role deployment, it is important to ensure that each server has a minimum amount of memory for efficient use of the database cache. There are some scenarios that will produce a relatively small memory requirement from the memory calculations described above. We recommend comparing the per-server memory requirement you have calculated with the following table to ensure you meet the minimum database cache requirements. The guidance is based on total database copies per-server (both active and passive). If the value shown in this table is higher than your calculated per-server memory requirement, adjust your per-server memory requirement to meet the minimum listed in the table.
Per-Server
DB Copies
|
Minimum
Physical Memory (GB)
|
1-10
|
8
|
11-20
|
10
|
21-30
|
12
|
31-40
|
14
|
41-50
|
16
|
.