Programmer time is a factor that comes into play when you build something and re-training your people to use a stack they are not familiar with + the associated mistakes can get expensive in a hurry.
If you happen to be familiar with the MS stack and are able to factor the license fees into your business plan there is no strong reason against and many for using that particular stack.
MS programmers tend to be a bit more expensive than people working with one of the many Linux offerings but that's not such a huge difference that it would become the deciding factor and if anything the MS stack is more performant than the Linux one on the same hardware (and I write that as an anti-MS guy, I strongly believe that politics and tech should be kept separate when it comes to discussing systems relative to each other).
So even if there are lots of reasons why I would not have made that particular choice I can completely understand why the SO people made their choice the other way.
Keep in mind that it hardly ever is the webserver that is the bottle neck.
My theory on why this is the case is very simple: MS can afford to throw vast amounts of money at optimizations that are next to impossible in Linux simply because the coupling between the layers in Linux is looser. And that's a good thing, it translates into better security and fewer bugs.
As always, optimization alone is not a reason enough to go down a certain path. But for raw speed on requests it's fairly hard to beat IIS, if that's what you're after (I'm usually not, and even when it matters I can comfortably saturate most outbound links from a single server doing light processing, and as soon as the processing becomes the bottle-neck the CPU cache size, RAM and so on matter more than your OS, but given identical hardware a 'dirty' approach should yield better results at a cost of unreliability/complexity).
Tight coupling and money are a good arguments, thanks.
However, i believe we are comparing apples to oranges here. IIS uses it's own kernel module, HTTP.SYS - http://www.microsoft.com/technet/prodtechnol/WindowsServer20...
So, looks like having specific kernel api optimized for your particular usecase is an advantage, which IIS has and others don't.
There is a good reason majority of the World-Wide-Web is run on 'Nix stacks -- and there is a good reason majority of servers in general are 'Nix stacks. Also, an overwhelming percentage of super-computers (I know we are talking about webservers, but it illustrates performance capabilities) are running a 'Nix stack.
There is also cost involved, as well as flexibility of the stack. With a 'Nix stack, it's infinitely flexible, not so much the case with a Microsoft stack. Also the default MS Stack comes with a lot of additional OS overhead that is not present in the 'Nix stack, which reduces any said box's scalability.
Without trying to turn this into some sort of flame war - I was merely trying to suggest that the MS stack was not/is not the best choice for a highly scalable website. Take the top 10 websites -- they all run on 'Nix. The top cloud providers (except MS Azure), all 'Nix. These are companies that can easily afford MS licensing, so that's not part of the equation.
A MS stack at this scale is unusual to say the least.
That's not to say it won't scale (as evidenced by the SE team), but it doesn't mean there isn't a better alternative that saves more money and scales better with less hardware, etc.
It will be very hard to get into a flamewar with me supporting the Microsoft side of things. That said, none of the links you posted prove anything regarding performance, they do prove something about total cost of ownership, which once you factor everything in leans towards Linux for most installations, however, just looking at the situation for SO seems to me to suggest that they were more comfortable doing the initial development on the stack they were most familiar with and when the license costs started to count against them they used Linux machines to scale out.
Which is a pretty smart decision. Whether an MS stack at this scale is unusual does not say anything at all about whether or not it performs well.
I think we agree for the SE team, given the founders were MS stack familiar, it makes sense.
However, I have to disagree on your assertion the 'Nix's are less performant than the MS stack. The top tier web companies are not running 'Nix because TCO is lower; for most of these companies licensing costs are negligible and if it helped to scale better, it may even save them money going with MS stack... but they don't go with a MS stack...
Sometimes a RHEL license can even cost more than a MS license. Couple that with an Oracle DB back-end, and you easily have a much more costly setup than the MS equivalent. It's not about the money.
These companies are choosing the 'Nix stack because it is performing in an entirely different level than the MS stack. Everything from tiny embedded systems with 64k ram, up to monster systems with TB's of ram.
> "I Contribute to the Windows Kernel. We Are Slower Than Other Operating Systems. Here Is Why."
http://blog.zorinaq.com/?e=74
IMO, it has one of the best tooling sets of any platform out there (Visual Studio) which saves lots of programmer time and increases productivity. With BizSpark the initial cost argument is out...so how's that not pragmatic?
I'm biased of course, but I think it worked out pretty well.
If you have extensive Microsoft experience and take advantage of something like BizSpark* (although one suspects with their connections they wouldn't have needed that) it's hard to see how it wouldn't be plenty pragmatic and inexpensive.
* Currently three years of free licenses, all software you download during that time is free forever, and discounted MSDN subs thereafter.
