W3WP Process High CPU and RAM utilization on Exchange 2010 CAS

Last weekend I updated Exchange to SP2 and UR3 and have been keeping an eye on the server occacionally to make sure its running normal.  Today I noticed in the Exchange Server Performance Monitor that there was a lot of spiking and more than normal activity.  The extra activity was for the processing, so I went into the task manager to take a look at what process was using it all, as we normally run between 5-10% utilization on this server, and it was spiking up to 60% at times and consuming over 1GB of memory.

I checked out the Event Viewer and didn’t see any errors.  There were quite a few warnings from ActiveSync for an iPad device for user dsims, could this be linked to the IIS process issue?

Next I downloaded Process Explorer and located the troubled process and gathered some more info.  The IIS worker process was linked back to MSExchangeSyncAppPool.  I went into the Performance Graph and noticed something odd, there was a lot of CPU usage and IO and then it stopped, and started again.

At this point, I did a google search for ‘MSExchangeSyncAppPool high memory usage’ and many pages linked back to an issue with iOS devices.  Since I know who has the iPad in our company, I messaged them to see if they could take it offline for a while to see if that resolved the issue, which it did.

My concern is why was this process so heavily used?  Was it a bug, was the user downloading all of their mail, what caused the issue?

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