Let's say it's something like Stack Exchange that I'll be running (it isn't, but it's close enough to have similar resource usage), and I'll have approximately 20000 users from August to January (with many more after that time).
The network this will be hosted on is pretty decent (25/25 Mbps) and the infrastructure is good (there hasn't been a power outage in years).
Does $5000 seem like a reasonable amount to expect to drop on the hardware, or should I look at a larger or smaller amount?
Also, how should I treat the tradeoff between raw specs and server-grade hardware (given a limited budget)?
For hard drive space, I'm planning around 10 to 15 TB in software RAID 10.
As far as power, I'm thinking two PSUs (beyond wattage, is there anything specific I should look for?) and a $100 or $200 UPS for good measure.
What I'm less sure about is the CPU/RAM/mobo I should be looking at to scale like this.
One possible approach would be to arbitrarily pick something like two 12-core Opterons and 96 GB RAM then decide that sounds good,
or I could allocate a certain amount of money toward this then just max out the specs within that bound,
but I'd like to be reasonably scientific in my approach.
So, what kind of CPU/RAM/mobo setup would you recommend and why?
Also, clustering. If not for the initial system, is clustering something I should look into later (e.g. when I need to upgrade / scale up the system), or are there better ways of accomplishing that. Clustering is something I really have no experience doing, but the server OS is going to be Ubuntu 10.04 if that helps in tailoring any advice.