C# sends SQL data 4 times less from one box than from another

Posted by Bobb on Server Fault See other posts from Server Fault or by Bobb
Published on 2011-02-24T15:15:46Z Indexed on 2011/02/24 15:26 UTC
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W2003, .NET 3.5, SQL 2008

I have prod and UAT app servers deployed in 2 different data centres. I have a C# app which reads text file, parse the text and sends the data to the SQL in bulk.

SQL server is in US and the app servers are in London (but in different places). All POPs have dedicated network connections. There is no public internet involved.

When the app runs on UAT server I can see in Perfmon that the Send byte/sec is x4 higher than from production server. My estimate is that one server outputs at 1 MB/s and the other at 250 KB/s rate.

My suspicion immediately is that there is a router on one of the DCs which shapes traffic or does QoS limitation on traffice from London to US.

However support and Windows team and networkig team all are saying that there are no differences in neither networking config on the 2 DCs nor NIC config on the 2 app server...

How to find out why is the networking bottlneck is 4 times tighter in one place than in the other? What can I do about it?

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