The TLDR version of this article, is yes you can.
Altaro VM Backup by default will always leverage Microsoft VSS (Volume Shadow Copy Service) in order to get an application consistent backup of your virtual machine, which is especially important for highly transactional apps such as Exchange, AD and SQL.
To ensure that this option is enabled you can go to [VSS Settings] and ensure that [Application Consistent Backups] is enabled.
Altaro VM Backup can backup both active and passive DAG nodes. It’s recommended however to move the active databases to one of the DAG nodes and then perform a backup of a passive node, thereby reducing and minimizing any possible impact to your live environment. If you have one DAG node that’s always set as a passive node, have Altaro backup this node. This will eliminate guess work and would be the ideal setup as you would avoid having to move the active databases to a specific node before a backup is taken.
Another recommendation when backing up DAG nodes is to increase timeout values in order to avoid failover between DAG nodes. It’s possible that you experience a VSS timeout, which results in a failover from the active node to the passive node during checkpoint creation process.
You can use the following commands in order to increase timeout values:
cluster /prop SameSubnetDelay=2000:DWORD cluster /prop CrossSubnetDelay=4000:DWORD cluster /prop CrossSubnetThreshold=10:DWORD cluster /prop SameSubnetThreshold=10:DWORD