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I owned a MacBook Pro with an original Apple-certified SSD. I erased my entire disk (using the erase option in disk utility) with TRIM disabled, then reinstalled the Mac OS and enabled it as soon as when I got into the system. Would my previous data still be trimmed?

Model: MacBook Pro 2017 13", running Mac Sierra. SSD name: APPLE AP0256J Media

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  • Please detail what type of MacBook Pro (model, year, size, etc.) you have. This makes a vital difference for the answer.
    – jksoegaard
    Nov 21, 2021 at 23:19
  • @Rukord Do you have the version with 2 Thunderbolt ports or with 4 Thunderbolt ports?
    – jksoegaard
    Nov 22, 2021 at 10:41
  • The one with 4 thunderbolt ports.
    – Rukord
    Nov 22, 2021 at 15:30

1 Answer 1

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First, it is not the data per se that is TRIM'ed - it is the locations where the data is stored seen from the point of view of the operating system.

If your computer had been running a more recent version of macOS with APFS boot drive, it would automatically TRIM all unused locations at every boot. However, your computer is running a historic version of macOS that does not have this feature.

I would highly recommend upgrading your computer to a recent macOS version such as macOS Big Sur or macOS Monterey.

As far as I know, the macOS Sierra program for creating a new file system on disk ("mkfs") does not TRIM out the data blocks now considered empty.

As a quick fix, if you do not want to upgrade macOS, you could create a huge file on your disk taking up all disk space - and then remove that. It would trigger a TRIM of all the now empty locations on disk.

You can create such a huge file by running this command in the Terminal:

dd if=/dev/zero of=hugefile bs=1m

Then the command completes (i.e. the disk runs out of free disk space) - remove the hugefile file.

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  • Thanks for your information. What if I upgrade to Monterey and then do an erase, and install an older version of Mac OS (such as Sierra)? Will TRIM still work in this case? Edit: To be more clear, that was exactly my case. When I did the erase the first time, it was on Monterey. I erased it and reinstalled the OS, which automatically prompted me Sierra so I installed it without thinking too much. After that I erased it again and installed the Sierra again. That time I had very limited knowledge so I was not sure what to do exactly, but to destroy my old files as much as possible.
    – Rukord
    Nov 22, 2021 at 21:26
  • Upgrading in order to erase and reinstalling an older OS doesn't really make sense here - it's much easier to simply erase on the old OS. What is it you're trying to achieve here actually? - Are you looking for some kind of performance boost? - Or?
    – jksoegaard
    Nov 22, 2021 at 21:28
  • I didn’t upgrade it on purpose. My case is that I was using it normally and one day I’d like to sell it. It was on Monterey already that time and I erased the SSD. After that I reinstalled the OS which is Sierra and did the same thing again. I already sold the laptop to someone and I’m afraid that the guy could potentially retrieve my data but once TRIM Command was triggered, it became very hard. So I wonder if my data could still be recovered at a consumer level (I don’t think he’ll bring it to a forensic lab just to recover my data).
    – Rukord
    Nov 22, 2021 at 21:43
  • If you run the command in my answer to create a big file of zeroes that fills up the disk, and then remove it afterwards (while still on Sierra with TRIM enabled) - that should be good enough for "consumer level deletion".
    – jksoegaard
    Nov 22, 2021 at 21:55
  • Thank you for your detailed explanation. I still wonder another thing: will erasing option in Disk Utility trigger Trim in HFS+?
    – Rukord
    Nov 26, 2021 at 6:03

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