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They admit in the article that a lot of this performance could be an illusion caused by the APFS instant cloning feature, which essentially just creates a new directory listing pointing to the existing file when you copy a file to the same volume. A separate copy of the data is only made when you make a change to one of the files.

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It also appears that it doesn't copy the whole file upon changing one of the files. It only stores the changed portion. I assume this is block level. Pretty cool. But yes, SSD speed has very little to do with copy speed in this case.

I wonder if this could be used to infer information that users may not intend. For example, perhaps copying a file and fraudulently altering something in it at a specific time could be used as evidence in a trial.

The speed seems to be accurate for a high capacity PM981 or newer especially in raid Apple is just using bonker fast SSDs.

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