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big_smile Author

Level 1

45 points

Copying files to external drive - File size is not the same. Should I be concerned?

I am backing up my Mac to do a complete reinstall*

Here are some files I have copied to an external drive. The left is the external Drive. The right is the source file on the Mac:

If you look everything is the same:

• The MB value at the top of the window (289.6 MB)

• The Size value in bytes.

The only thing that is different is the size value in MB (335.8MB on disk).

Should I be concerned? Has it copied over properly?

This seems to happen with a lot of copies, but other copied files match up perfectly.

* I already do daily back ups to Time Machine, Backblaze and Carbon Copy Cloner. The reason I am making manual backs ups, is because when I do a reinstall I don’t want any preferences or other such non-file things copying over, which is what I gather happens with things like restoring from Time Machine.

OS: 10.14.6

MacBook Pro 15″, macOS 10.13

Posted on May 22, 2022 4:16 AM

Top-ranking reply

MartinR

Level 7

21,697 points

Posted on May 22, 2022 7:25 AM

Your file count & size match, and the copy (the external drive) has the larger "on disk" space used ... that would indicate to me that the copy process is ok.

There could be a number of reasons the "on disk" size differs, especially if the two disks are different formats ordifferent sizes.

There is a very nice app called Visual Differ in the Mac App Store that will compare folders & files on different disks. I use it all the time to keep multiple external disks up to date and verify they are identical. It color codes differences, making it easy to visualize any folders or files that are not identical. You could use that to verify all the files are the same.

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Copying files to external drive - File size is not the same. Should I be concerned?

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