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I bought a 6TB (5.45TB usable) to transfer my 3TB drive.

I used robocopy source destination /MIR /R:0 /W:0 /xo

Robocopy reports that 2.228TB were copied, but I only have 1.18TB left available out of the 5.45TB.

My 3TB is drive is NTFS, and my 6TB is exFAT, but I don't tink that it matters.

I tried “Disk cleanup” and “Clean up system files” but both report nothing to clean.

Why am I missing so much space and how to retrieve it?

Giacomo1968
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freddoo
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2 Answers2

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"My 3TB is drive is NTFS, and my 6TB is exFAT, but I don't tink that it matters"

Yes, it matters.

Your allocation size is critical here. Change your file system to NTFS or exFat, both need to match. Or, set the unit size as small as possible. I suspect you left the settings on default. Otherwise, each file, even the smallest file(e.g. 1kb) will be 4096KB once transfered. If you were to do the math, you would get the amount of gigs shown in your log report.

In conclusion, the easiest solution is to match file system format. Both NTFS or both exFAT.

Giacomo1968
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Full Array
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I did tried the 128kb AUS, but it still took an extra Tb, I guess I have to many small files.

The simpler solution was to format my 6tb drive to NTFS, recopy everything and the transfered size was the same as the original.

Thanks for your help

freddoo
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