I am thinking of a possible web server set up for our web project at a datacenter. We will have at top 1 million unique visitors per day.
We will do light jobs mostly like rendering pages, our "hardest" task would be generating a single page PDF report for users when they request and charging money from their credit cards when they do purchasings.
Which one would be more a more clever and stable way of doing it:
A single server that holds either web server (apache, php etc) and database (mssql)
Two servers, one holds web server(apache, php etc) and another server for database (mssql).
Also you can recommend your own idea of ideal setup :)
A bonus question: Would it be more clever to buy our own servers and buying co-locationing or directly buying dedicated server from datacenters.