Transaction Log Truncation Failure for MSSQL Instances on Shared VHDX

When attempting to run a backup job for a Microsoft SQL Server that is in either a SQL Server Failover Cluster or AlwaysOn Failover Cluster with a shared VHDX, the backup job reports the warning:

Failed to truncate transaction logs for SQL instances: <>. Possible reasons: lack of permissions, or transaction log corruption” or SQL log backup job fails with “Regular database <> was not backed up in Oib

On the guest, within the %programdata%\Veeam\Backup\VeeamGuestHelper.log file, the following line can be found:

BACKUP LOG cannot be performed because there is no current database backup.

This is behavior by design:

• [For Hyper-V 2012 R2] Veeam Backup & Replication backs up shared VHDX disks in a crash-consistent state.
  
  Because the VSS subsystem is not involved in the backup process, the SQL Server is not aware of a backup having occurred and does not update the date of the last database backup. Due to this lack of an update to the last database backup entry, when the SQL Instance receives the command to truncate logs (“backup log”), it cannot find a corresponding database backup event and returns the error above.
  
  SQL logs truncation or backup is not possible in this configuration. Please change to using an AlwaysOn Availability Groups SQL installation with individual VHD(X) for each VM.
• [For Hyper-V 2016 and later] Veeam Backup & Replication does not support processing of VMs with shared VHDX disks. You must change the disk format to VHD Set (VHDS).