VBR Error: An item with the same key has already been added (Hyper-V)
This issue relates to a conflict with the HOST ID of a tenant’s Hyper-V host server in the VCSP database and can occur for multiple reasons. While there is no one-size-fits-all solution, there are potential workarounds and steps to diagnose the cause.
First, to determine whether there is a HOST ID conflict, run the following command on every Hyper-V host server included in the backup job:
wmic csproduct get uuid
Compare the UUID of each physical server. If one or more UUIDs are identical, the servers were improperly deployed by the tenant, likely by cloning rather than a clean install. The only permanent and proper remedy to eliminate the error is to recommend a full reinstallation of Hyper-V on all servers from the official Windows Server installation ISO media. However, since this is not possible in most cases, there is a potential temporary workaround.
This error only occurs when a backup job is configured for multiple VMs on different hosts to a cloud backup repository. If you want to backup to a local target with all VMs in the same job, the UUID conflict will not be an issue.
To enable the servers to backup to a Cloud Connect target, as a prerequisite, each Hyper-V server must be standalone and independently managed through the Hyper-V Manager. If the servers are configured as a cluster and the client is using the Failover Cluster Manager, the only solution is for them to create a new cluster and reinstall Hyper-V on all hosts. While we have not tried yet, it may be possible to backup a Hyper-V cluster to a local target and then perform a backup copy job to a Cloud Connect repository.
If the servers are not in a cluster, you can create separate backup jobs for each Hyper-V server. The UUID conflict only occurs when VMs from different Hyper-V hosts are included in the same job. While this workaround is not ideal, and it will not work with the Failover Cluster Manager, it will allow VMs on each server to be backed up successfully.