Duplicati says I have 20x more data than actual

I have just under 2.5 TB of data on my computer I’m backing up to Backblaze B2 with Duplicati. I started my backup, and it says I have 55 TB to go?! The weirdest thing is, I had tried IDrive before, and it said the same thing! Where is Duplicati getting this number from, and will it actually upload 55 TB of data? Because I will not be able to pay for that, that’s for sure. The file number is accurate, but the size is completely not.
(Screenshot from Duplicati)
(Screenshot from Disk Management of all my drives)

Any chance you have sparse links? OneDrive creates those. Also is deduplication & compression enabled? 20 x dedup would be a killer to get. Mounted SMB shares under NTFS ?

So OneDrive is off, but there are files in the onedrive folder, including many shortcuts. I excluded any onedrive folders, and any files containing onedrive. Would the sparse links be in those folders, or elsewhere?
I believe dedup and compression are enabled by default, no? I haven’t turned them off, that’s for sure.
And I don’t have any SMB shares.

Is there a way to rescan my computer, to see if the upload size changes?

I suppose you could use tree size or GetFolder Size and analyse disk usage. Pay attention to file size vs size on disk.

Recently on one of my ZFS data set I had 3 times usage of the file size and I confirmed it via multiple tools which was driving me nuts. I was on the verge of getting more drives only to realise I had 3 copies set on the ZFS data set.
If de-duplication is in use you should see file size greater than size on disk.

Try creating 1 job for each drive and see on which one you get disk usage mismatch. That will help you narrow down the issue.


Narrowed it down to drive G:, which I use primarily for storage of my phone’s data, as well as a backup of Google Photos. Both WinDirStat and TreeSize say the drive has 383 GB of data, which is accurate. When I try backing it up though, Duplicati says it’s 54 TB. I’m going to try backing up individual folders within the drive to narrow it down further.

Found the problem! I have some files backed up from my phone, which I compressed with File explorer’s “compress contents…”. Each photo and video claims to be 20 GB, but only take 4 KB of disk space. ~2,500 “20 GB” files add up to 50 TB…
In addition, almost none of them actually open - they throw an error of “Can’t read file header”. I have no idea how that happened, but at least now I know what’s going on. I can exclude this broken folder from backup, until I figure out what happened and hopefully recover the files.

Thanks @RaptorG for your help and suggestions!

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