Doubt about backup retention

[xv13rc]

Hi I'm new to PBS although I've been with PVE for a few years now, I apologize for my English.

My question is regarding how backups work internally in PBS: I have a backup task configured in PVE so that I retain a single backup of each VM/LXC, these backups (so far) are stored on a hard disk in ext4 format. I want to try PBS for its incremental copy and deduplication feature.

If I keep the hold on to one copy per machine, how does PBS work? Does it completely delete the old copy first and make the new copy from scratch? Or does it first check what data from the previous copy it can reuse so as not to copy them again?

Greetings and thanks

 

[xv13rc]

By the way, some LXCs have bind mount to a z1 raid where I have my personal files, I say this because I don't know if it's relevant.

 

[TErxleben]

PBS works like rsync+dedup.

 

[xv13rc]

PBS works like rsync+dedup.

That means that it does not delete the last backup and make a new one but reuses the data from the old backup, right? I know it may seem like a redundant question, but I'm pretty confused right now.

 

[TErxleben]

That's the way it is. Unknown data blocks are only added by the PBS. Old and superfluous blocks are only collected during a garbage collection and deleted by prune. It works differently than with a vzdump.