Frequent DAG failovers in a virtualized Microsoft Exchange environment on VMware vSphere

Running Microsoft Exchange in a virtualized environment provides a lot of extra flexibility and even increased availability when running in a HA configuration. This short article is dedicated to some extra tuning that might be necessary in your environment.

The environment I’m talking about is consisting of 2 virtual Exchange 2013 servers, running on VMware vSphere 5.5. Storage is provided by an iSCSI-based array. Compute by HP Gen6 Intel-blades.

Ever since these servers are running, a failover is triggered by the Microsoft Cluster Service, failing all the active mailbox databases over to the second Exchange server. It seems that a snapshot creation task is triggering this failover. As we are using Veeam for backups, we contacted them to ask if there are any workaround for this issue.

Veeam released this following KB article, telling you how to decrease the cluster sensitivity and prevent the failovers to happen. In our case, these settings sadly didn’t solve our issues.

What seems to be the problem, are dropped network packets from within the Guest OS. Following this KB article by VMware, it seems there are some issues with the VMXNET3 NIC on systems that have high traffic bursts (like Exchange).

For now, these settings seem to solve our issue and no failovers are happening again, but if it arises again, I will definitely update this article.

Hopefully both possible solutions by Veeam and VMware can help you in case you are running into the same issue.

Got feedback? Please leave it below!

Transforming from baremetal VMware vSphere to nested VSAN: Part Two (Preparation and Execution)

Welcome to part two of my VSAN ‘trilogy’! If you’ve missed the first part, see the link below.
Transforming from baremetal VMware vSphere to nested VSAN: Part One (Design)
This post contains the steps I’ve taken to prepare my transformation from a traditional vSphere lab environment to a VSAN-powered environment.

Continue reading