How to prune backup storage after change in retention policy?

Hi there,

I have been testing Duplicati for a couple of months now and absolutely loving it. I am running on canary ( which I have been finding really stable, and loving the new features.

I have one question however. I started creating backups with “Backup Retention” set to “Keep all backups”. However I have realised that for my needs, and storage capabilities that won’t be feasible, so I have changed the backup configuration to the new “Smart backup retention” policy.

My question is now this - my backup storage (which is being achieved very simply using SFTP to a FreeNAS ZFS volume) hasn’t reduced in size since changing this option, yet I must have dozens of daily backups that can now be pruned from the tree. I’ve tried “Compact Now” but that hasn’t made any difference.

Is there an easy way I can apply the new Smart Retention Policy to an existing backup set? Or is there a way I can manually prune the backup store so that I can get the size down?

Many thanks,


Hi James,

The retention policy is applied automatically after each backup run. No need to do anything in particular :slight_smile:

The reason you may not see any change in size can be because the deleted snapshots contained nearly the same files.

Two almost identical backup runs will use the same files on the backend and therefore add almost no new files. This means that if you delete one you may see as little as 10-20MB of space freed because that’s the space used by only that snapshot.

An additional reason you may not see space reduction is because the removed data is inside a volume with other data you’re still using. Duplicati will clean up these volumes when enough filess inside are marked deleted but it’s expensive to clean up each time any data is deleted so it’s delayed.


Awesome - thank you for your help! I can confirm that this is working as you described - just took me a while to get my head around the numbers but all looks good. Thanks again!

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