Copy on write - APFS vs HFS+ behavior

My question is whether or not copy-on-write cloning is implemented on files residing on an HFS+ (Mac OS Extended) formatted drive.

If you are running an APFS-based version of macOS, and copy or duplicate a file that is on an HFS+ drive (copied or duplicated to that same HFS+ drive), is the resulting copy/duplicate a new file that is independent of the original ... or is it a copy-on-write clone?

(Copy-on-write was introduced a few years ago with APFS & High Sierra; all subsequent releases of macOS use APFS. For anyone wanting a primer on copy-on-write, here's an informative article -> Copy, move and clone files in APFS, a primer.)

Posted on Mar 16, 2022 7:38 PM

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James Brickley

Level 5

5,970 points

Posted on Mar 20, 2022 1:16 PM

JHFS+ is still the same, nothing has changed. If the files are on an HFS+ volume then they would behave the same way they always did prior to APFS. The copy on write and cloning only applies to APFS. So no, duplicated files on HFS+ are not cloned instantly they are physically copied.

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Copy on write - APFS vs HFS+ behavior

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