Wanting to convert an external HFS+ drive to APFS. This is said to be doable without losing the current content. I have no reason to doubt that. But I'm curious:

Is there any reason (any significant difference) to instead do a fresh erase/reformat? (and then restore the contents from backup)

  • Is there a reason for the conversion? Is the external drive an SSD? If not, you’re not likely to see any benefit from doing this. HFS+ is still a solid partition scheme especially for external drives.
    – Allan
    Dec 16, 2022 at 21:32
  • Also, see this answer on what happens during the conversion process. It is a “format in place” so there’s no difference.
    – Allan
    Dec 16, 2022 at 21:37
  • A real reason to do it is for Volume support, regardless of SSD or spinning disk. You also get improved Time Machine if you're using it for backups.
    – Ezekiel
    Dec 17, 2022 at 4:02
  • Not using it for backups. For very large libraries that do not change often. So the APFS trick of re-using identical blocks might save a tiny bit of space.
    – WGroleau
    Dec 17, 2022 at 6:13


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