Prune job effectively deleted all backup revisions, why?


the following prune job left my hard disk with 2.9/3 TB free space. I started a radical prune job because before it was almost full. Now after the prune it is empty, is it my mistake?

What I did is:

Options: [-log prune -storage LocalStorage -all -exclusive -exhaustive -keep 0:1]

Thx. Now, let’s go for maaaany hours of backing up again…

This is because you ran prune with a retention clause (-keep) and -exclusive - these two things together are dangerous, as the latter allows the removal of the last backup, whereas a normal prune ensures the last backup is always kept. Don’t run -exclusive when you don’t have to, it’s unnecessary.

Also, I’d suggest that keeping only one revision (-keep 0:1) kinda defeats the purpose of having a reliable backup - you may as well just use a sync tool, which can of course render your backups useless if you get attacked by ransomware.

Don’t worry about keeping lots of revisions - the whole point of Duplicacy is to de-duplicate data such that incremental backups include only changed data. The extra disk space is normally very minimal.

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I was having theory in mind, but wanted a restart.
Regarding “don’t worry”: I often rename files/folders for better organisation - Duplicacy is not doing additional backup of the pure file contents, right?

Mostly, correct.

There may be a very small amount of overhead - where file contents are computed to have unique chunks (hashes) but these are at file boundaries so most of the changes will just be metadata. Renaming a 1TB folder, for instance, might only incur an additional MB or two at most.

Plus you can ‘optimise’ a heavily rearranged storage at any time by using the -hash flag once.

Just choose a sensible prune retention period that will allow you to restore e.g. daily, weekly, monthly backups going back a year or so. You’ll likely find your de-duplicated and compressed backup storage, with all those revisions, actually takes up less space than the data you’re backing up.

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