SQL Performance related to ASYNC_NETWORK_IO

If your application is working with SQL and you face performance problems, I guess one of the things you do is to try and see the current processes in SQL

If by running “select spid,blocked,lastwaittype,cpu,physical_io, memusage,status, cmd from master..sysprocesses” you see process that is waiting on ASYNC_NETWORK_IO than this means that you have network or client application problem that is causing SQL to not be able to flush its data (in general, client is not working fast enough to get the data and the buffer are filled)

In this blog post I would like to focus on network issues and I assume your application is good.

To ensure your network is correct check the following:

Your NIC has latest firmware
Your NIC is set to specific speed and duplex – this is because from time to time we see problems that are related to card that detected the wrong speed / duplex mode, suggest to have it set to the maximum your network can hold
Your NIC is working properly – no errors in event viewer or general problem in system that looks as related to network
the component that are involved in the communication between client and server work correctly (Router, Hubs, etc) – check that you don’t have packet loss

Hope tis post will save you few hours Smile