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I wanted to try out apfs, therefore I formatted my external HDD with it. Now the partition table seems broken. How can I reinitialize the drive?

My goal is two create two HFS+ partitions, each 1TB on the drive. I decided to wait with migration to APFS as it is not supported by all my devices.

See attached screenshots the 2TB HDD shows up as a 4TB drive?

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The drive is a Seagate FireCuda Compute 2TB, SATA 6Gb/s (ST2000LX001)

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I've done this, on an SSD at least.

Probably on your drive right now there's some kind of corruption going on; I'd bet that Untitled and CRE are sharing the same UUID... I've had that happen with some interesting results.

If you want two partitions, with one as APFS:

  1. Reformat the whole disk, creating two partitions - the one you want to be APFS should be formatted as HFS+.

  2. Once that's done, format the HFS+ volume as APFS. That will create a container, and then the final volume will be inside that.

In the pictures, you can see I have three partitions. In the first image, it's apparent that there are four volumes, and the two under "Container disk1" are APFS.

If you want two APFS volumes:

  1. Reformat the whole disk - that the disk level, as in disky, not disky1 - with one HFS+ partition. You could go straight to APFS but I think this will prevent potential issues...
  2. Format the whole disk as APFS. You should then have a three level tree - disk, container, and volume.
  3. Now you can create your second APFS volume. Select the "Container" disk, click on the "Edit" menu in the menu bar, and click "Add APFS volume." That will create what behaves as a second partition, but it will share available disk space with the first APFS volume.

You can set minimum and maximum sizes for the volumes too if you like.

Disk Layout

Partition Layout

  • Hi Fin, sorry I clarified my original post..My goal is two create two HFS+ partitions, each 1TB on the drive. I decided to wait with migration to APFS as it is not supported by all my devices. – florian Sep 30 '18 at 19:15
  • Well, seeing as this is still titled as a question about APFS, I'm just going to let this stand... @florian, best of luck to you - I think erasing and reformatting will fix you right up. – Fin Hirschoff Sep 30 '18 at 20:08
  • I cannot erase, as the HDD is perceived as a 4tb drive now this leads to an internal error :( – florian Oct 1 '18 at 6:01
  • In this case if you haven't, try these: – Fin Hirschoff Oct 1 '18 at 14:20
  • I should be careful with the return button. If you haven't, try 1. Delete a partition if it lets you; erase the drive. 2. Use the command line utility dd - if you aren't familiar with it: be careful, because you can erase anything, or everything, your pick, by accident. Some people call it "data destroyer." But if the disk in question is still disk2, you would unmount the volumes, then do this: 'sudo dd if=/dev/zero of=/dev/disk2 bs=1m count=256' - that would zero out the first 32 MB of the drive (256 Mb). That might do enough so you can fix this back in Disk Utility. Be careful with dd. – Fin Hirschoff Oct 1 '18 at 14:41

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