Understanding Back Pressure in Exchange 2007

October 18, 2007

in Exchange, Microsoft

If you’re an administrator of an Exchange 2007 organization then you should familiarize yourself back pressure. 

So what is Back Pressure?

“Back pressure is a system resource monitoring feature of the Microsoft Exchange Transport service that exists on computers that are running Microsoft Exchange Server 2007 that have the Hub Transport server role or Edge Transport server role installed. 

I got a call from a client the other day and they were panicking because their Exchange 2007 server stopped sending and receiving external mail.  I remembered from a previous incident involving the back pressure feature and had them check their Application Event Log for Event ID: 15002.  There it was…Back pressure strikes again.  Back pressure was activated when their disk utilization climbed above 84%.  Even though they had over 4 GB of disk space free on the C drive…the percentages are what Back Pressure takes into account.

In a multi-server configuration back pressure is less likely to come into play.  This feature often activates in single server designs where all the roles are installed on one server or there is only one HUB server. 

Keep this in mind the next time you are building your Exchange 2007 organization with only a single server or single HUB Transport server.

For some more information on Exchange 2007 Back Pressure click here.

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