What Are the Hardware Requirements For My Server?

Question

What are the hardware requirements so that the sites hosted on my server will run smoothly?

Answer

cPanel's server requirements can be found here:

Installation Guide - System Requirements

However, those are the requirements for the cPanel software itself to run smoothly. If you have moderate to heavily trafficked websites, you should plan for more resources than the baseline requirements.

For a website, one page view equals one process, and that process uses a variable amount of CPU and RAM. This means that if you have 10 concurrent users one day and 100 the next, the site's RAM and CPU requirements increase by a factor of 10 in a single day.

To calculate the server hardware you actually need, use the following:

S = your system's hardware resources (CPU / RAM / IO speed / network throughput)
X(n) = a site's resource use per hit — this varies by site, by URL within a site, and even over time on the same URL
C = the concurrent process count generated by hits to your sites
D = the resource use of the system's core services
T = the cumulative resource use of X, C, and D

So: (X(1,2,...) * C) + D = T

If T < S, the server will run smoothly. If T > S, the server becomes slow and unstable.

To calculate this accurately, your administrator would need to profile all sites on the server to determine per-hit average resource use, then either optimize the sites to fit more on one server or move to a server that can handle your desired T value.