Unable to restore VM from S3 backup node: count (1) not equal to backup images [] count (0)

Symptoms 

Unable to restore VM from S3 backup node:

SVM_ERROR: cannot restore the virtual server "6faa3fdf-c0ab-4687-9904-edff5c6d0236": failed to collect restorable disks: domain disk [{device:sda imageFormat:qcow2 path:/var/lib/libvirt/images/411/0}] count (1) not equal to backup images [] count (0)

Cause

Try to restore from backup with virtio driver to VPS with scsi driver and reverse. The disk have a strict structure:

CONFIG_TEXT: virt-filesystems -a /mnt/sda3/94/0 --all --long --uuid -h
Name Type VFS Label MBR Size Parent UUID
/dev/sda1 filesystem xfs - - 5.0G - a971cfc6-a12f-4051-909e-2d63c8ca4630
/dev/sda1 partition - - 83 5.0G /dev/sda -
/dev/sda device - - - 5.0G - -
 

When change scsi to virtio, there is a change in the target and the bus:

• For scsi:

CONFIG_TEXT: <target dev='sda' bus='scsi'/> on S3 backup sda.qcow2.zst

• For virtio:

CONFIG_TEXT: <target dev='vda' bus='virtio'/> on S3 backup vda.qcow2.zst

Resolution

This is not a bug. It is by design. This is the way that we define and determine Disk driver for the VPS.