Incremental message for PBS backup

May 20, 2017
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When creating a backup of a VM not previously backed up to PBS, 'backup was done incrementally' is almost always shown:

Code:
INFO: backup is sparse: 2.83 GiB (1%) total zero data
INFO: backup was done incrementally, reused 4.91 GiB (2%)

I take it 'incremental' means space was 'reused' as the backup is sparse. Maybe you could consider not using the word 'incremental', as claiming an only technically incremental backup is incremental can be quite confusing.
 
Last edited:

ph0x

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Jul 5, 2020
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PBS splits all backup data in chunks. You probably have a similar VM, which was already backed up, so those chunks could be reused.
And on a side note, therefore your backup was incremental. ;)
 
May 20, 2017
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Netherlands
cyberfusion.nl

oversite

Active Member
Jul 13, 2011
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I understand, and while that is technically true, I think the message is confusing from a practical standpoint :). See here the first question about this message: https://forum.proxmox.com/threads/first-backup-of-pve-vm.82871/#post-364565
I don't follow, for me incremental is the perfect word here, how is it confusing you? Incremental means for me the changes between now and the previous backuped data. It's easy to understand and also true. What bothers you here?
 

ph0x

Renowned Member
Jul 5, 2020
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That it was the first backup of a specific VM, therefore no data of that VM could have been backuped before.
But taking into account the way the backups are stored I agree with you that this is the correct term.
Might still be a bit misleading for beginners, though.
 

dcsapak

Proxmox Staff Member
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Feb 1, 2016
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just fyi, the sentence:
PBS splits all backup data in chunks. You probably have a similar VM, which was already backed up, so those chunks could be reused.
And on a side note, therefore your backup was incremental. ;)
is not completely correct.. while it may be that the backup shares blocks with already existing ones, for privacy reasons (e.g. untrusted backup server), the client does not actually
know about chunks from different backup groups

the reason that on the first backup something like
Code:
INFO: backup is sparse: 2.83 GiB (1%) total zero data
INFO: backup was done incrementally, reused 4.91 GiB (2%)
can happen, is that not only zero chunks are reused, but all
so if a chunk repeats in a single backup, it only gets uploaded once (so here it seems that an addition ~2GiB was from chunks that repeated)
 
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