Not enough space on destination drive

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Posts: 1
Joined: 9 Mar 2024

BlueCalcite

I have two identical 12TB hard drives -- one was shucked and is in my desktop holding data, and the other I use externally to back it up once a week. It's time to back it up again. Windows reports that there's 231 GB of 10.9 TB free on the internal drive, and 631 GB free of 10.9 TB on the external. It stands to reason that there is about 400 GB of data to be copied over. However, when I try to synchronize/mirror the internal drive to the external, FreeFileSync states that there is 889 GB to copy, which obviously isn't going to work. Where could this discrepancy be coming from and how do I resolve it?