Improving mod_perl Driven Site's Performance -- Part I: Choosing Operating System and Hardware Page 3
You want an OS with good memory sharing capabilities. If you preload the Perl modules and scripts at server startup, they are shared between the spawned children (at least for a part of a process' life - memory pages can become ''dirty'' and cease to be shared). This feature can reduce memory consumption a lot!
And of course you don't want an OS that doesn't have memory sharing capabilities.
If you are in a big business you probably do not mind paying another 000 for some fancy OS with bundled support. But if your resources are low, you will look for cheaper and free OSs. Free does not mean bad, it can be quite the opposite. Free OSs can have the best support you can find. Some do.
It is very easy to understand - most of the people are not rich and will try to use a cheaper or free OS first if it does the work for them. Since it really fits their needs, many people keep using it and eventually know it well enough to be able to provide support for others in trouble. Why would they do this for free? One reason is for the spirit of the first days of the Internet, when there was no commercial Internet and people helped each other, because someone helped them in first place. I was there, I was touched by that spirit and I'm keen to keep that spirit alive.
But, let's get back to our world. We are living in material world, and our bosses pay us to keep the systems running. So if you feel that you cannot provide the support yourself and you do not trust the available free resources, you must pay for an OS backed by a company, and blame them for any problem. Your boss wants to be able to sue someone if the project has a problem caused by the external product that is being used in the project. If you buy a product and the company selling it claims support, you have someone to sue or at least to put the blame on.
If we go with Open Source and it fails we do not have someone to sue... wrong -- in the last years many companies have realized how good the Open Source products are and started to provide an official support for these products. So your boss cannot just dismiss your suggestion of using an Open Source Operating System. You can get a paid support just like with any other commercial OS vendor.
Also remember that the less money you spend on OS and software, the more you will be able to spend on faster and stronger hardware. Of course for some companies money is a non-issue, but there are many companies for which it is a big issue.
The OSs in this hazard group tend to be developed by a single company or organization.
You might find yourself in a position where you have invested a lot of time and money into developing some proprietary software that is bundled with the OS you chose (say writing a mod_perl handler which takes advantage of some proprietary features of the OS and which will not run on any other OS). Things are under control, the performance is great and you sing with happiness on your way to work. Then, one day, the company which supplies your beloved OS goes bankrupt (not unlikely nowadays), or they produce a newer incompatible version and they will not support the old one (happens all the time). You are stuck with their early masterpiece, no support and no source code! What are you going to do? Invest more money into porting the software to another OS...