Asterisk Sizing guide


Does anyone have Asterisk sizing guide, i mean what hardware/cpu/memory and number of servers are required for a particular setup.

I need to setup IP PBX for 50 users which will increase to 500+ users. Trunk lines will grow accordling.

Is this going to be single server setup or I need multiple servers ?

If 50 users require single server, do I need to add more server when number of user increases ?

If multiple servers are required, are they going to be Publisher and Subscriber ?

Does Asterisk require a DATABASE for this increased number of extensions and user login credentials ?

How will Dialplan work to make all servers like single entity ?