tomkmvp:
Although a vehement condemner of those that use web gardens I hadn't seen that link before Tom thanks for that.
(web gardens rant = on)
About the link personally I think that this is a problem all of Microsoft's/IIS teams making. The implications are there that make it sound like it will help, it is in the GUI, in the performance section even. Really this should have been a metabase only (none GUI) feature as there are so few times it is used legitimately and it is abused frequently.
And this is further confused by the published authors on IIS that talk about web gardens. As much as I like Stanek's writing style and in fact the only IIS books I own are from him. I dislike the tone of which he (and others - not singling him out by any means) refer to web gardens as a useful and positive thing. Sounding technical but really not truly understanding the seldom benefits for it.
I was not surprised the old IIS team of Wang and co had a lot of questions about it as the amount of articles/books/etc referring to gardens in a positive light. I can only think they did not know enough on the subject and had to write something on the subject and it was always going to be positive. Often many of these books don't give any useful performance tuning advice at all (and it doesn't help the more MS line/myth that IIS is tuned by default) and the ones they do like web gardens are just wrong.
(/web gardens rant = off)
To answer your question about the downsides of it. Well they are real world ones that most article/authors don't have the same experience of. Like has been stated the Inproc stuff is one.
The main one is the administration and troubleshooting of the web gardens.
It can be confusing following multiple wp's of the same site. You do not know which wp is problematic when you have a problem. You are making life more difficult for no reason and what annoys me is some think it is improving the situation to have these gardens.
Also there is a small memory (and CPU) overhead when you have an additional wp rather than keeping it in the same one. But these are very small.
In theory you could overload stuff when you have multiple wp's as the before meaningful safeguards of memory consumption, etc are now not as meaningful as you have multiple processes and you could have a scenerio if you are not careful when you could overload stuff. Where as in normal usage it is not a problem.
Occasionally it is useful in the real world for testing (but only testing) in the case of a runaway memory wp. When an app/wp fails you give the illusion that others are still working. But this just masks the real issue in hand that the app is problematic and a poor mans band-aid fix.
There are no benefits 99.9% of the time apart from certain cases which you are not likely to see.