Title: Slow Backup Performance with Commvault Agentless Backup on XCP-ng Cluster

[yeopil21]

Hello,

We are currently experiencing very slow backup speeds when using Commvault's agentless VM backup in the following environment:

Environment:
Commvault Server - Windows server 2019
Hypervisor: 3-node XCP-ng cluster
Shared Storage: NetApp iSCSI SR
Backup Solution: Commvault (v11.36.49)
Backup Method: Agentless VM backup
Backup Target Storage: NetApp NFS volume

Issue:
When backing up virtual machines via agentless mode, the transfer speed is extremely slow—just a few MB per second—resulting in backup jobs taking several hours to complete.

No significant load on the VMs being backed up
No bottlenecks observed in Commvault job logs
All basic network(1Gbps) and disk performance checks look normal

Questions:
Are there any known limitations or bottlenecks for Commvault agentless backups on XCP-ng environments?
Which parts of the backup flow (e.g., VM snapshot, disk read, CBT parsing) typically cause performance issues in agentless mode?
Any recommended best practices or settings to improve agentless VM backup speeds in this setup?

[olivierlambert]

Hi,

I think the best first approach is to ask Commvault. It might be interesting to compare with XO to check if it's the same ballpark numbers for backup speed.