Backup with or without "-hash"

I usually run my backups without using the "-hash" option. However every now and again I run a backup with the "-hash" option just to check that everything is backed up.

My backup are running fine without problems and today when I ran my backup without -hash there was no changes and therefore nothing to backup. Right after, I ran the backup with the -hash and to my surprise duplicacy backed up about 1.6 GB of chunks (of a total of 65GB).

Does that mean my normal backups without -hash, do not back all my files.

What does that tell me? Can anyone explain to me what is happening.

Cheers and thanks

Does this previous topic answer your question?

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Thanks for the link. I am not sure if it answers my question or even if I have a problem, but I am assuming that the reason for uploading much data by using the -hash is due to the 2nd issue as mentioned in your link. I have about 300 or so small files (50-150Kb) that change nearly every day, so by using the -hash I am filling up the “holes” in the chunks and thus need to upload these new chunks. It makes sense in my scenario. Now I just need to consider if I should run -hash backup more often or less often.

Thank you very much for you asistance.

From my own usage (2 windows machine and 1 mac) i can say that -hash was never needed. I’m doing restores (of the latest revision) about once every 3-4 months, and so far all the files in the backup match the files on the drives.

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Ok… Thank you for the feedback. Sounds good. I am not aware that I have any software which does not modify the file timestamp so not using -hash should not be a problem. The only software I have ever used which does not modify the time stamp is Veracrypt (or Truecrypt) but there is also a setting to let it change the timestamp. As I currenly am not using Veracrypt then I should not have any problems not using -hash.

Again… Thank you both for the responses and feedback… truly welcome.

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As a side note: regardless of the --hash option, duplicacy is currently not performing as good as it could when it comes to small files. See here:

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