I believe the point is that it doesn’t do a snapshot stun or run out of a delta disk. Its a different technology. I know it does use qm snapshot. The tech docs I’ve read don’t quite fill in the details for me either. Much of the point of PBS architecture was to avoid that stun.
The proxmox_backup_client is not my bag. I’m glad it’s found a user. Most pros I know don’t touch it.
Let me explain the ‘pro’ comment. I’m active on the official forum. Most of the ‘pros’ there don’t use proxmox_backup_client. People I respect do not use that tool, probably each for their own reasons.
My own issue with PBS support for physical servers is that full recovery is DIY. You have to format disks and stand up at least a temp OS in order to wipe and start over.
I think I’ve scaled out PBS pretty far. My biggest datastores are 14 TB. That’s about 85 VMs. I use a multi-layer PBS setup for Backup and Sync at 5 geographic locations. A couple sites have hardware syncing to virtual, which in turn does site-to-site. I’m using PBS site-to-site sync to support a colo migration.
PBS is a great tool in rapid development. During the time I’ve used it, they introduced fleecing and all its many issues. There are more changes coming. As admins, we are supporting a moving target.