[fChk]

Regarding a squid cache in front of the web server: I think this could work out very well, but I had a bit of trouble finding a proper tutorial. I know the tutorial I'm looking for is out there, but I can't seem to get the right results out of google. Every search query I try gives me the same thing: How to set up squid as a proxy server for accellerated web browsing. The squid config file is like a small novel. I could probably figure it out just reading the config and comments, but it'd take a long while. Any suggestions on this would be appreciated.

Never had to use squid so, I'm afraid, I can't be of any practical help there. Nginx has a built-in caching mechanism, why not take advantage of that? I'm not aware of how much familiar you are with Nginx, but it has more -features- than meet the eye if you dig deep into it.

I'm aware that you're trying to build a distributed system (located on 3 nodes) but setting Nginx on one node (let's say VPS-2) and PHP-FPM + DB on s1 might also work.

In this scenario, Nginx and PHP-FPM will be link via HTTP (instead of a socket) via a TCP/IP socket (instead of a unix domain socket),  PHP-FPM and the DB will share s1's CPU and Nginx will be left with the full power of the less powerful VPS-2 CPU and the weaker block device I/O-wise. s0 will remain and you can use for memcached doing whatever you want it to do OR mount its storage remotely for use in VPS-2, improving the I/O there.

Not sure if that will work but its a possibility among others. Just keep testing...


PS: for what it's worth:
https://duckduckgo.com/?q=squid+linux+proxy&ia=web

@fitkoh

Edited: I had to re-login to edit the crossed section in the text. It's getting hard to write an error-free piece of text without a cup of coffee first :-)