So, my "sugar daddy" datacenter is kicking me out. This is where I have been hosting absolutely free for a decade so I have nothing bad to say about them... at all. :-) My 4U quad-core2duo, 4GB RAM, 8TB SATA beast will soon become homeless.... Did I mention they let me host that monster for free?
This website was a minor task for that server but last Sunday I moved it onto a minuscule "cloud" VPS at Gelsys. Running PHP and MySQL on 256MB of RAM (and no swap) and expecting a stable server under load did require some tinkering. I am not going to detail every little thing. I'll only outline the basic setup.
I have Wordpress spitting out static html files which is what is being served for 99% of all requests. PHP is only being called on to re-generate the files when the caches expire and to serve up the admin interface. In this way my mini-VPS can handle a pretty decent amount of traffic. I don't generally get a lot of traffic but I am curious to see how the server behaves during a spike.
Wordpress caching is handled by the excellent W3 Total Cache plugin which recently got official support for Nginx. Yay! no more custom rewrite rules. My only problem getting it running this time was that it refused to cache the index page, which is kind-of bad when it is one of the heaviest pages to render. Turned out it was a simple precedence issue. "/" is considered a folder which I caught in a rule before the caching rules had a chance to do their thing.
Nginx is the web server. I have been running it for a few years already but for this it is absolutely essential to save on ram and get the best performance serving static files.
PHP is called from Nginx over an unix socket and served by php-fpm. PHP is compiled with my favorite accelerator eaccelerator. It is just the simplest to get going and has shown good performance for my apps. PHP has been scaled down a lot in php.ini, reducing mainly memory usage and timeouts.
MySQL loves memory so I had to do the equivalent here. Basically taking the standard performance tips and doing the opposite. I know I will only server Wordpress and I know I don't have any enormous datasets so MySQl should be fine on very low memory. Also since I limit the number of php processes I consequently limit the maximum number of client connections MySQL will need to keep track of.
The only other service running is ssh and I was surprised to find that sftp was one of the biggest memory hogs. Uploading a bunch of files of sftp and the server would immediately come dangerously close to running our of memory. In fact it did a bunch of times during my tweaking.
I have been thinking about switching from Wordpress to some static website generator but that is for another time. This setup looks fairly smooth at the moment.