Incorrect file size

[borgmac]

Brand new Mac mini M4 with Sequoia 15.1 is giving me a different file size on disk.
Here are some tests, never got the same amount on disk!
But the 3 files are opening well (using minivmac)
I first thought it was the binary vs decimal, but 267 390 976 bytes / 1024 / 1024 is 255 MB. That's not what I see...

MacOS753.cdr
M1 Mac mini Original (Monterey)
267 390 976 bytes (267.4 MB on disk)
M4 Mac mini transferred with Migration assistant (Sequoia)
267,390,976 bytes (244.3 MB on disk)
M4 Mac mini manually copied from M1 (Sequoia)
267,390,976 bytes (275 MB on disk)

Is Sequoia using a different method to calculate the space on disk?

 

[Bigwaff]

Do these file sizes all come from the Finder in Sequoia? The Get Info dialog?

 

[gilby101]

The 267,390,976 is the number of bytes in the files. That these are identical gives some confidence that the files have copied correctly.

The "size on disk" is something different and is, as it says, the space on disk used by the files. Sequoia in both your cases is calculating it in the same say. The space on disk is frequently less than the number of bytes due to APFS functionality like compression, clones, sparse files, and extended attributes. Occasionally it is more - copying over a network can contribute to this. The size also depends on the method of copying - from your results, Migration Assistant is better able to make use of APFS optimisation than (and I am guessing what you did) a drag and drop in Finder from a network share.

So it is not that Sequoia is using different methods to calculate space on disk, rather it is that Sequoia will vary in how it optimises copying and storing processes. This has always been true with APFS format volumes, but it has been optimised with most major upgrades.

Don't worry about the differences you are seeing unless you have evidence that the file content is different.

 

[borgmac]

Do these file sizes all come from the Finder in Sequoia? The Get Info dialog?

Yes, it is

 

[borgmac]

The 267,390,976 is the number of bytes in the files. That these are identical gives some confidence that the files have copied correctly.

The "size on disk" is something different and is, as it says, the space on disk used by the files. Sequoia in both your cases is calculating it in the same say. The space on disk is frequently less than the number of bytes due to APFS functionality like compression, clones, sparse files, and extended attributes. Occasionally it is more - copying over a network can contribute to this. The size also depends on the method of copying - from your results, Migration Assistant is better able to make use of APFS optimisation than (and I am guessing what you did) a drag and drop in Finder from a network share.

So it is not that Sequoia is using different methods to calculate space on disk, rather it is that Sequoia will vary in how it optimises copying and storing processes. This has always been true with APFS format volumes, but it has been optimised with most major upgrades.

Don't worry about the differences you are seeing unless you have evidence that the file content is different.

Thanks a lot for this very clear explanation. I was thinking it must have been something like that. On the M1 Mac mini, the partition is also APFS. Does that means that Monterey is not compressing files? It could be also that it was not an APFS partition when I copied that file originally on the M1 Mac mini.

 

[gilby101]

Does that means that Monterey is not compressing files? It could be also that it was not an APFS partition when I copied that file originally on the M1 Mac mini.

I put it down to the APFS driver being tweaked over the years since first introduced. The boot disk with Monterey would have been APFS.

 

[zevrix]

but 267 390 976 bytes / 1024 / 1024 is 255 MB. That's not what I see...

Apple is using 1000, not 1024.