Scaling issue with IIS 6 and ASP.NET

Hi

Has anyone experienced scaling issues with IIS 6 and ASP.NET web services?

A client application's response time was recorded when invoking a simple web
method (it simply returns). A single test client invokes this method
synchronously without a delay between a response and the next request. An
average time in the order of 11ms is measured. The web service is not
servicing requests from any other client apps. When a second test client is
run concurrently with the first an average time in the order of 22ms is
measured. The median however remains fairly constant between these two
cases.

The CPU and memory usage remains fairly constant but the average response
time more than doubles! It looks like IIS itself is actually not scaling
very well. I've tested with IIS6 and IIS5 and IIS6 scales notably worse.

Thanks

I'm not certain how your experiment says anything about IIS6 not scaling...

If my test clients are sending many requests as fast as it can, if CPU
remains fairly constant as I add test clients, I would expect the response
time to increase proportionate to the number of clients I add.

Think about it this way -- Suppose:
- Server at 10% CPU utilization is doing able to do 1000 units of work per
second
- Servicing one web request requires 10 units of work
- Client makes 100 web requests for an average response time of 10ms per
request
--> I add a second client, which is also able to make 100 web requests in a
second
- Now, you say the CPU remains "fairly constant", so it's still at 10% and
able to do 1000 units of work per second. However, there are now 200 web
requests coming in, and since each takes 10 units of work to complete,
you're asking for 2000 units of work when the CPU is only doing 1000 units
of work per second -- i.e. on average, the requests are going to take twice
as long to finish..


The more interesting question to me is why CPU isn't doubling its
utilization to keep the average response time of 10ms in the face of twice
the number of requests. There seems to be a bottleneck of some sort, and
until you locate the bottleneck, you don't know what isn't scaling.
- What is your CPU utilization during this experiment?
- What's between the clients and servers (regarding network bandwidth)
- What's the RAM on the server?
- Are requests being queue'd on the server?
- Is your web service somehow synchronized?

--
//David
IIS
This posting is provided "AS IS" with no warranties, and confers no rights.
//
"Rivaaj" <rivaajj.TakeThisOut@na.com> wrote in message
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Hi

Has anyone experienced scaling issues with IIS 6 and ASP.NET web services?

A client application's response time was recorded when invoking a simple web
method (it simply returns). A single test client invokes this method
synchronously without a delay between a response and the next request. An
average time in the order of 11ms is measured. The web service is not
servicing requests from any other client apps. When a second test client is
run concurrently with the first an average time in the order of 22ms is
measured. The median however remains fairly constant between these two
cases.

The CPU and memory usage remains fairly constant but the average response
time more than doubles! It looks like IIS itself is actually not scaling
very well. I've tested with IIS6 and IIS5 and IIS6 scales notably worse.

Thanks