Increasing Exchange 2010 DAG Failover Threshold

Recently I encountered an issue with a client where VEAM backups were causing the DAG to fail over. This has led me to question whether or not VEAM is truly supported by Microsoft. I’ll need to scour for some Microsoft documentation to actually confirm. Either way, I digress as that is for another conversation in itself.

It seems that when VEAM is committing the snapshot the FCS sees the machine as down and in turn the DAG fails to the secondary site. In order to resolve this issue  I have found that you must decrease the sensitivity of the FCS polling. This entails increasing the failure threshold as well as the frequency in which FCS polls.


You can set the maximum values via cmd prompt on the mailbox servers in question:

cluster /prop SameSubnetDelay=2000:DWORD

cluster /prop CrossSubnetDelay=4000:DWORD

cluster /prop CrossSubnetThreshold=10:DWORD

cluster /prop SameSubnetThreshold=10:DWORD


Let me know how this goes for you.


One thought on “Increasing Exchange 2010 DAG Failover Threshold

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