Why migrate from IIS6 to IIS7?

Question

I have a number of web apps running on several IIS6/Server 2003 boxes. They run well and are happy. They are all asp.net web apps and use .NET 3.5.

What, if any, would be valid reasons for contemplating moving the web apps to IIS7/Server 2008?

Answer 1

1. Eventually, Microsoft will discontinue Server 2003 support. Admittedly, that won't be for several years, so it doesn't impact you today.
2. Improved support for ASP.NET MVC. This is probably the big one for most of us. You can get ASP.NET MVC working on IIS6, but there are some hoops to jump through.

I'd give you more, but I myself am not yet on Server 2008 yet, and have nothing else to give. Presumably Vista (which I do use, both at work and at home) has the "same" IIS7 as 2008 does -- the UIs certainly look very similar -- but I wouldn't consider my experience there to be useful to your question.

Answer 2

Ability to write pipeline components in managed langauges. Previously, if you wanted to write an ISAPI filter to handle a certain type of web request, you'd have to write it in C++. Now, you can use good ol' .NET code. This allows more customization with the ability to write reusable pipeline components for handling various types of request. For example, all .js file request are routed to a ScriptCompressor pipeline component which zips and returns them with lots of cacheability set up.

The improved support for MVC is linked to this as you can set II7 to route requests without extensions to .NET so you can have urls which are "cleaner" such as http://www.yourwebsite.com/customer/1 without having any extension visible which reveals what type of server technology you're using and is very untrendy these days.

Answer 3

IIS7 is rewritten from the ground up with a concept of being "pluggable". IIS7 is more extensible than it ever has been before. The entire request pipeline has be reworked to allow you to more easily work with requests, as well.

From a performance aspect, these changes are immediately recognizable. You can run sites developed for IIS6 in a "Classic" application pool that will preserve compatibility, but provide a noticeable performance boost. In the non-scientific evaluation that we have done so far, our legacy application has seen about a 20% reduction of load times on our IIS7 test machine.

Of course, the reason we have to run in "classic" mode is an interesting side note. Inside the global.asax, there is some pre-fetching on application start which touches the HttpContext. Specifically, there is pre-caching done, which IIS7 does not allow. So, before we can switch from "classic" mode, there are some changes that we will have to make.