The web server world is basically a three-way battle between an established giant, Apache, the speedy alternative, Nginx, and IIS, which isn’t used all that much in commercial web hosting. Apache and Nginx are both excellent options, but there are a number of other web servers worth consideration. The leader of the pack among the less-well-knowns is LiteSpeed, a commercial web server with an open source version that combines many of the advantages of Apache and Nginx.
A major benefit of LiteSpeed is — as the name suggests — speed and resource efficiency. That’s because of the way LiteSpeed handles requests. LiteSpeed has an event driven architecture rather than the process driven architecture of Apache. Process drive web servers will fork a new process — create a new worker — for each incoming requests. Each of those workers takes up a substantial chunk of the server’s resources. Event driven architectures don’t spawn new workers for each request and, therefore, are substantially more resource efficient.
The results of this difference in handling requests can have a significant effect on the resource efficiency of a server. RAM use is typically a small fraction of that used by Apache. That has two main advantages. Firstly, under heavy load, your web server is far less likely to grind to a halt and start swapping. Secondly, resource efficiency means less expense for hardware. If, for equivalent traffic, a site uses less resources, you save money. A supplementary advantage is that, as a web host, your infrastructure goes further.
Now, if you’re familiar with web servers, you might be thinking that sounds pretty much exactly the same as how Nginx works. You’d be right; Nginx operates in basically the same way, although there are low level differences. But LiteSpeed has an advantage over Nginx because it can act as a drop-in replacement for Apache. That means Apache config files, Apache mods, and various other components work with LiteSpeed. From the perspective of a web host, that means you get the resource advantages of Nginx with Apache compatibility.
So, for a website that runs Apache and is struggling with the workload, there are a couple of choices. Firstly, the site owner could upgrade to a more powerful physical server. Or, secondly, they could swap out their Apache server for LiteSpeed. This isn’t going to solve every performance problem, but it will definitely lead to more efficient resource use without having to completely reconfigure the server to make it work with Nginx.
And, not to blow our own trumpet, one of the major advantages of the Apache compatibility is that you can use LiteSpeed with InterWorx.