We are going to do a multi-server test environment and wanted to know from community experience what servers should be the most "powerful" and which server can be on the lighter end.
For this we want to setup the following:
Once this is proven to work we are going to want to add additional LDAP, Mailstore and MTA servers. Once tested to work this will be deployed rather quickly and on a large scale to host email for our clients. So it must have scalability in mind.
We have the following machines available for test and will purchase similar server grade systems for deployment.
1x 8 core (upto 16gb of memory)
2x 4 core (upto 8gb of memory)
2x 2 core (upto 8gb of memory)
Also, from community experience is Linux soft-raid an acceptable solution?
Your archiving servers are simply mailstores, so you can treat them one in the same. You will simply state that you want archived email to go to a specific mailbox server based on CoS settings.
Power of the server really depends on the load you are going to experience. They all need power in the right places. MTA needs power to be able to ensure mail flows through without getting backed up in queues. Mailbox servers need power to ensure users have a fast experience when they are getting mail, and also to ensure that the MTA's don't get backed up. That being said, there's no canned answer.
Re: soft-raid, everyone has their own opinions on it. Personally, I've been burned on firmware bugs/issues with hardware raid in the past few years, that I've been preferring software raid over hardware raid. If the machine has enough CPU, it won't be an issue. CPU's are fast enough these days to handle it without an issue. But that's a topic bound to start a flame war. In my experience, it has worked perfectly well.