Architecture Evaluation

Am in the process of proposing a .NET architecture for a client who wants to rewrite his website from ASP to .NET

Proposed architecture:
ASPX Code behind --> Web services --> Business Component --> Database Component --> Stored procedures --> Database

Web Services will be used to communicate between the presentation layer and application server.
The technology is ASP.NET, VB.NET on COM+ and Oracle on Unix box.

Expected concurrent users is about 3000! For this kind of hit rate, what should be load balancing support, hardware and software support, server configurations?

What are the technical risks in implementing this architecture that can be identified and raised now?

Any pointers and inputs would be very useful.
Thanks,
Jemima.

Wow! This looks like such a cool project!

I have done a similar architecture as yours for a web enabled planning system, but never on this scale.... The biggest problem we had was that our web server wasnt powerful enough. Nothing much we could have done about it either since we were using classic ASP. Classic ASP does not support cross server state management, so we couldnt use load balancing services. You on the otherhand will be able to do this using ASP.NET!

We only had problems when someone selected a huge report... Then the system crawled to a standstill... Most of the time, the page just timed out...

eliminate the Web Services part, that will slow down your performance a LOT, web services should only be used to give functionality to an outside app/web page
if its all done internally, eliminate the web services to remove the obsticle of boxing/unboxing of all data passed across laters.
if you must pass information between laters, look at .NET remoting instead of web services per-say

Thanks for the posts..

Shunt... yes I've suggested the web servers and applications servers be network load balanced in the proposal.. but never been part of or witnessed setting up such environment before.. although I've programmed for this sort of environment. Some network expert here may be able to throw some light on home capacity planning is practically calculated and done..

Kovan.. yes you're right.. but we did consider both remoting and web services option and decided on the latter as its much easier to implement.. and any other systems within this clients's domain may reuse these services later... and abt boxing/unboxing we intend to define the interfaces using datatypes like datasets, string, decimal, int etc

What do you think about session management? Although I prefer to suggest session state management mode to be in the database, for now I've recommended sticky sessions where the session management is Inproc. This is cos I wasn't sure if the database could be Oracle... has anyone tried this? Is session management support extended only to SQLServer and not any other database?

Oracle also has session support. They have always had it from at least Oracle 7.3! However, I have had really bad experience maintaining application state through the db.... I wouldnt recommend it. I would think your db should provide stateless functionality, dealing with bulk data and not session specific data... I think your business objects should be handling state.