I wouldn't look at user count as the driving factor. I'd focus mostly on the type of functions that the system is going to be supporting. MRP for a hundred thousand SKU's??, an e-commerce site dumping in thousands of orders a day?? a warehouse management solution picking/packing thousands of orders a day??
Also, if you are a big shop and AX is going to be a mission critical system, then your approach to hardware is going to be a little different than the regular company. As a solution architect, I'm not comfortable when a client is sharing a mission critical environment for TEST, DEV, and PRODUCTION etc.. What if a developer mistakely shuts down the Production server when installing a hotfix? Now, the 50 sales/customer reps just lost all their order screens, and shipping scanners go down with it. So, risk mitigation is going to define whether you have one or multiple environments.
Here's a simple view of a hardware deployment for 100 AX 2012 users running Finance/HR/Procurement/Sales Order/Projects/and lite manufacturing.
- Database server: 16GB o 32GB - Dual or Quad core CPU
- Portal Server - 8GB to 16GB - Sharepoint/AX Enterprise Portal/Role Center/Reporting Services - Dual Core CPU
- AOS Server - 4 to 8GB(Go 16GB, if you run PROD/TEST and DEV on the same box)
- Terminal Server - Min 4GB for the OS, and around a 100-200MB of RAM per concurrent user. Could be higher if they are using work/Excel and other apps. Will need a cluster for the TS as I won't put 100 users on one server. - Dual Core or Quad Core CPU
So, you've got about 4 servers now. They could all be virtual images, but I would give each image it's on set of disk spindles, whether those are local drivers or a SAN.
Where I've seen performance issues has been around hard disk performance and configuration of SQL Server. Makes sense to have dedicated spindles and RAID configurations especially for the SQL SERVER. It's going to cost you some cash here in order to meet the drive requirements for SQL... Cost could easily reach 15 to 45K for a SAN, and even more.
This should get you thinking about where you need to go.
Cheers!!
