You create a backup plan of a Hyper-V virtual machine using Agent for Hyper-V (agent on the host). In What to back up, you select Disks/volumes and then select individual disks or volumes you want to back up.
When recovering this VM or using the 'Running a virtual machine from a backup (Instant Restore)' feature, you encounter issues:
- you notice that disk layout does not correspond with the original machine
- restore/instant restore fails with this error:
Error code: 26542128
Message: Failed to get the ID of the boot disk.
Error code: 26542127
Message: Operating systems are not found.
System reserved partition must be included in the backup, otherwise volumes logic is incomplete.
Use 'Entire machine' backup level: in What to back up, select Entire machine.
If you want to do a disk-level backup, add the system reserved partition to the backup or perform backup of the whole disk instead of the volume where OS is located. See this article for step-by-step guidance.