Source size vs Backup size difference


Just wanting to know why the source size and backup sizes are different. I understand deduplication but didn’t expect there to be over 150GB of the same stuff. See my screenshot below if someone could help me out that would be awesome.



I’m a newcomer to Duplicati and this community, but I think I can help with your question.

I believe that the difference that you’re seeing in size between Source and Backup is completely normal and is probably due to both block-based deduplication and compression

This article explains how block-based deduplication works in Duplicati 2.0:

FWIW, my Source and Backup sizes are very similar to yours (Backup size = 60% of Source size)

Hi there and welcome to the community! :slight_smile:
@city_zen is completely right - the difference is due to deduplication and compression (in normal cases duplicati uses zip-compression).
Sometimes the backup could even be bigger than the source - when you delete source files/dirs they still are in previous versions of your backup that are still at the destination of your backup job (until retention kicks in and delete this versions too)

So all is as it should be :slight_smile:

Hey Guys,

Thanks for the explanation that clears things up so much. I’m super impressed at how much it’s compressed. That’s amazing :slight_smile:

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