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We have 2 servers for IIS with Load Balancer and 2 clustered MS SQL servers. Each servers has aprrox. 262GB RAM, 64 core processor(not all physical cores), etc. I mean servers are really powerful. The very strange problem i am experiencing is this :

When I publish my application to IIS servers it just works fine and super fast. But after 10 minutes or so, servers suddenly slow down. When I send a request to a page in my application it just waits about 20-50 seconds and then the page shows up. I researched about the issue a lot but I cannot come up with anything that will solve my problem and i cannot tell that the problem occurs because of IIS servers or MSSQL servers.

There are two images that describes server architechture below and also some extra information about the application and servers.

[Server Architechture]

enter image description here

[Network Storage Architehture]

Network Storeage Arc. Picture

  • OIBS_APP_1 and OIBS_APP_2 are IIS Servers
    • OIBS_APP_1 have Hyper-V installed for Domain Controller.
  • OIBS_DB_1 and OIBS_DB_2 are MS SQL servers(clustered)(for disaster scenarios)

  • Application that we run on these servers are running just fine on other servers that's ten times less powerful.

  • Application is Asp.Net web application.
  • Application uses "Asp.Net State Service" for web farm/garden.

So what I am asking : - What can cause this kind of slowness on the application? What are your comments and opinions about this situation? What should I do?

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Try running perfmon on the servers. Add counters for Logical Disk/Current Disk Queue Length, Processor Time, and Memory Page Faults/s. That should tell you very quickly if there are any "hardware" issues. – Chris S Jan 4 '12 at 13:48
Out of curiousity, have you run the query (TSQL) being first sent from the application front-end to the database, directly against the database (SSMS) and compared the query times? Can you quantify "super fast" and do you know what is happening during the 10 minutes when things go from super fast to slow (what queries are hitting your database)? – jl. Jan 4 '12 at 14:29
There are no hardcore queries that's hitting the database from the application within ten minutes. It's an intranet application and i am the only one who tests it after i publish.(It did not go the production yet.) Let me put it this way. There's a transcript(university degree calculation) query that runs on my local machine around 30 minutes. That query runs on the sql server directly from SSMS takes about 2 minutes. (Please don't judge the query or execution times. :)) – ward87 Jan 4 '12 at 14:36
Like i said there's no problem in the application in the first 10 minutes or so. Requests processed instantly. But after aprox. ten minutes when i enter the url from my browser it just waits about 20 to 50 seconds and then respond the request. – ward87 Jan 4 '12 at 14:40

I'd download the SPA3 tool from Microsoft, let it do most of the analysis for you.

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I am curious about the word "publish" here --- what happens when you do that? Does IIS reload? What queries are processed in that ten minutes. If you reload/restart IIS without touching the database, does the application get fast again? It sounds to me like you have some increasing amount of garbage in the .net system which can not be freed. Is the application container using more and more ram?

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