I rent a dedicated server for one of my sites (Linux, WHM/cPanel). The site gets a decent number of monthly visitors (over a million), and I am starting to wonder how I should monitor it to discover when a server upgrade will be needed.
Obviously I could wait until the server starts to crash a lot and the site starts loading very slowly, but I would like to avoid reaching that point, having a better way to monitor things.
1. Is monitoring the server load on WHM enough to know whether or not an upgrade is needed? On my case average server load is 0.5, and the server has 8 cores, so is this enough to say I probably don't need an upgrade?
2. Is there some other metric I should pay attention to to evaluate this?
Thanks in advance.