Does creating more websites on a single machine increase the number of requests it can handle?

Question

This is pertaining to Windows machine running IIS. Our operations staff have taken an existing website/application and created a second website/application, new folder app pool, the works, stating that there will be better throughput. I've NEVER done anything like this in the last 15 years of being a software developer in the .NET space and this just doesn't feel right. The original site was working fine and now with 2, it feels overly complicated and clumsy. Are there any best practices in this area that I don't know about, that can either approve or deny what they have done?

I'm going off to test by hand i.e. shutting one set down and logging the requests and responses and then turn them on, then compare my findings.

Any guidance would be helpful.

-Stephen

Answer 1

If anything you would create multiple workers for the application pool, not another site. And generally when doing this it's to work around code issues you don't control, as you sacrifice things like cache hit ratios and while causing overall higher memory usage and lots of duplicated work.

In almost all cases, it will lower the throughput.

Tell them this: Stack Overflow and the rest of our Q&A network can run off of one server, with a single application pool that has a single process. I don't think the problem is in (or solved by changing) your IIS configuration.

Answer 2

As Nick pointed out, the few advantage that are attained by doing this will very likely be surpassed negatively by the extra IO load on the server; especially since you created a new website not just increased workers.

Each 'thread'/worker stacks more and more load on your server with each worker taking up extra headroom over and above the original code... the processing time per request will at best be the same, very likely though it will be worse.

Your colleagues' approach is like forcing a slow horse to carry more stacks of hay without trying to make the stack lighter to see if maybe it would start running instead of walking... The lighter stack comes from more efficient code and implementation. Only after this should you start thinking if its worthwhile to increase the number it carries per trip.

You can find some tips and tricks to make IIS apps more efficient in these articles: https://msdn.microsoft.com/en-us/library/bb742459.aspx

http://forums.iis.net/t/1148571.aspx?IIS+6+performance+tweak+guide+draft+

These are for older versions of IIS but most concepts still apply.