Domain vs Workgroup

Solution 1:

Is the workgroup model right for us?

For 3 computers? Sure, I might have looked at using a Linux box or Windows Home Server instead of Server 2008 to save on licensing costs, but for 3 users the need for a domain is most likely very low.

Should the number of users/nodes be the only factor to consider? I guess not. So, what other factos should we consider?

The number of users matters only indirectly. Usually you want a domain, when you need features you can only use with domain. Like Group Policies, Exchange, and so on. Lots of windows server functionality and MS Servers only work well in a domain environment. But for a really small number of users it is very rare to actually need those features.

If those other factos point to a workgroup model, but the network becomes to big. How big should it be (in terms of users and nodes) in order to migrate to a domain model an take advantage of its benefits?

You will want to switch to a domain when you need to use a feature that can only be used on a domain. If you want some redundancy for that 2008 server you will want a domain. If you want Exchange you will want a domain. If you want users to be able to work from any computer instead of an assigned you may need a domain.

If you think you will be growing a lot, or think you will need some feature that only works in a domain in the future you may want to enable a domain now to save having to change things on your computers later.

Solution 2:

Using a domain makes many things easier (authentication and authorization to shared resources) but requires a certain amount of knowledge. I would recommend you do not set up a domain until you're prepared to have two servers dedicated to the Domain Controller role (no other roles and not hosted VMs). These don't need to be huge servers; single processor, 4GB RAM and a small RAID 1 will be more than sufficient. Setting up a domain also depends on how you're connected to the internet, if at all.

Just off the cuff I'd say it would be helpful to migrate to a domain once you have 10 nodes or multiple users per node. A domain would also be very helpful/required if you decide to host your own e-mail server.