that's relatively easy to explain, only the naming is doubled:
the backup-hdd are local disks raid1 in xcp-ng and there brought to xcp-ng as a local "vmbackup" volume, called vmbackup
on xcp-ng-volume a disk is created with the name "backup_raid1_1tb" and connected as 2nd disk (xvdb) to XO
ab68fa1c-49a8-4d15-afcf-ecdc8bcd9d04-grafik.png
to make the disk available for backup-usage the disk xvdb is mounted via "remote" as a local
now usage for backup-ng is possible, but the usage is not xo_disks