Why Does HDP for Business Start My Stopped Proxmox Virtual Machine During a Backup?
Applicable Products
- HDP for Business
- Proxmox VE
Scenario
You back up a Proxmox virtual machine that is in the Stopped state. When the backup starts, the Proxmox VE task log records a Start task for that virtual machine, issued by the user account that HDP for Business uses to connect to the host. It appears that the backup has powered on a virtual machine that you deliberately kept shut down.
Explanation
HDP for Business does not boot the guest operating system of a stopped virtual machine. To back up a stopped virtual machine, it places the virtual machine in prelaunch mode. In this mode, the QEMU process is created, but the guest operating system does not start and the virtual machine does not even reach its BIOS.
Prelaunch mode is required so that HDP for Business can use the QEMU Machine Protocol (QMP) to:
- Read the disk configuration and layout of the virtual machine.
- Read the Changed Block Tracking (CBT) data that identifies which disk blocks have changed since the previous backup.
Without this information, the virtual machine cannot be backed up consistently. Proxmox VE records the transition into prelaunch mode as a Start task, which is why the task appears in the task log even though the guest operating system never runs.
Details
- The guest operating system does not boot. The virtual machine does not reach its BIOS, and no application inside the guest is started.
- No network service of the virtual machine becomes reachable during the backup.
- After the backup finishes, the virtual machine returns to the power state it was in before the backup. A virtual machine that was stopped remains stopped, and a virtual machine that was running remains running.
- The Start entry in the Proxmox VE task log is expected behavior and does not indicate an unexpected power on.
- This behavior applies to backups triggered manually and to backups triggered by a schedule or an auto protection rule.
Further Reading
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