Enabling compressing (gzip/deflate) in the Apache server will reduce the size of the response but will add more CPU cycles, I will run a stress test with various response sizes but I wanted to ask if in terms of server load is there any suggestion on when should I turn compressing on or off?
Thank you
I think that as long as the server has a powerful CPU, use compression. Speed is usually the best feature that servers should have after security and stability.
In most cases web servers are limited by io (be it memory, network bandwidth, database, hard drive, ...), and have plenty of spare cpu cycle to use for compressing the pages before serving them, especially since this isn't even really that much cpu intensive, while it provide a huge usability boost for your users and save you bandwidth.
It depends on what you want to achieve. Tipically, turning deflate on won't add a very significant footprint to your CPU performance and if your website/s include large text files (html, js, css, etc.) it's likely to make an important difference in bandwidth usage and page loading times. Of course, if what you want is to reduce system load and don't care much for bandwidth, this wouldn't be the right choice for you.
Another option you might find useful is installing a lightweight web server/proxy like Nginx, lighttpd or Varnish (I personally prefer the first one), and serve compressed static content with that (leaving heavier Apache processes only to handle the dynamic content). That would also be likely to result in a better overall performance of your server. But, again, these all depends on your scenario, what's your website/web application like, and what you want to achieve.
