This question already has an answer here:
I'm building a quite simple web application, and need to get some rough understanding of how much load my server can take.
Of course, this depends on a whole lot of factors, but I just need a rough idea if we're talking about ten or ten thousand users, because at the moment I have no idea.
Standard LAMP-setup, with a quite small database and a reasonably simple and fast PHP. Each non-static request requires about 20 simple SQL queries. With no load, the runtime for such a request is around 50 ms. No explicit caching.
Current hosting is on a VPS w/ 1GB RAM and unknown CPU.
Is it possible to give a rough estimate given this? What is the bottleneck? CPU, RAM? Does 50 ms / request mean 20 requests per second? How much can caching help (factor 10? 100? 1000?)? Where would caching make most sense? How do I perform load-testing?
Uuh, lots of questions, not expecting detailed replies but would greatly appreciate pointers to where I can go from here to read up on system requirements/testing/possible ways of scaling up!