I'm trying to erase an external disk drive that I had been using as a backup disk. There are no options for me to securely erase - the option just isn't there at all.

It is currently formatted as MAC OS Extended (Journaled, Encrypted).

I have a second HDD drive that when mounted shows the security options when erasing.

Any ideas what is going on here? This is a new problem for me; I'm sure I've secure erased this disk before.

Edit: I've just noticed that the only difference between the two disks is that the one that could be securely erased is down as a 'USB External Physical Volume' whereas the disk I'm having the problems with comes up as a 'CoreStorage logical volume'. Is this the issue?

2 Answers 2


MacOS doesn't let you do a Secure Erase on encrypted volumes because there's no point: a single erase will delete the encryption keys; and any residual data on the disk will be meaningless junk that cannot be decrypted.

Multiple zeroing of a mechanical disk can put significant stress on it and shorten its lifespan.

Similarly, MacOS doesn't let you secure erase SSDs, because that's also a pointless exercise: doing the erase doesn't actually make it more securely erased.

Why is a secure erase 'not necessary' for SSD's?


I've found the answer, and I'm going to leave this question up in case it helps someone else.

The issue with the disk was that it had been encrypted. I needed to reformat it with no encryption for it to be recognised as a USB External Physical Volume instead of a CoreStorage logical volume. From there it can be securely erased as normal.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .