Challenge
During the snapshot creation or commit phase of a Veeam Backup or Replication job using vSphere, a primary node in a DAG cluster may lose the heartbeat long enough to cause a failover to the secondary node.
Cause
This problem is caused by the lack of connectivity in VMware vSphere during snapshot operations. Sometimes referred to as "snapshot stun."
Solution
The suggestions below are general advice intended to help alleviate and prevent issues. Every environment is different, and while these settings and suggestions may work in one environment, they may have little or no impact in others. Generally speaking stability issues which occur are often environmental, and will require investigation of all components involved, both physical and software.
The suggestions below include configuration changes to VMware as well as Microsoft Exchange. Veeam is not responsible for any issues incurred after making the suggested changes. You are advised to contact and review all setting changes with the respective product support organization.
More Information
Backing up just the passive node of a DAG cluster will still provide full recovery options. Provided replication of information is current between each cluster node, a backup of the passive node should still properly truncate Exchange transaction logs. Please confirm transaction logs are truncating after backing up the passive node. Then it should be possible to use Veeam Explorer for Exchange (VEX) to restore mail objects (2010 and newer).
