Is it safe to erase and resell an external SSD?

As pice of information worthy of reading

" Hard drives vs. SSDs

To securely erase data, hard disk drives fill the occupied space on the drive with a file consisting of zeroes or execute multiple writes of different characters; for more, see Securely wipe disk drives. Flash storage has an inherent limitation in that data may only be written to and erased from a given location a certain number of times. This number is typically over 10,000, but it's still possible a user could hit that limit over the life of the storage device.

To address this problem on solid-state drives, manufacturers use wear-leveling algorithms that evenly distribute data among SSD blocks, which means that data is constantly moved around on the drive so the blocks will be worn at an equal rate.

A side-effect of wear-leveling is that a file's data blocks aren't always kept adjacent to one another but could be distributed and disjointed. Wiping programs like DBAN  have a hard time identifying all the far-flung data blocks, so they don't do a good job of secure deletion on an SSD.

Standard secure deletion tools damage SSDs by performing an unnecessary number of additional writes without being able to tell where the data is written.

Using this method from Apple should be enough

Erase and reformat a storage device in Disk Utility on Mac

You will need to let the drive sit idle for an extended period to allow a built-in function called Garbage Collection to clean all the cells and prepare the drive for re-use.

No further actions are required for SSD drives

User wrote >>

"  Using this method from Apple should be enough."

No, it's not. I had already done all this, as I have indicated before: 'Initially I erased and formatted the way it's done with mechanical drives'.

Please read the last sentence in the link you provided, which is this:  Note: With a solid-state drive (SSD), secure erase options are not available in Disk Utility. For more security, consider turning on FileVault encryption when you start using your SSD drive."

That last part is if you are keeping the Drive not when selling the drive

If your were to Encrypt the Drive and sell it

The New Owner would not be able to use the drive at all.

User wrote >>

'' built-in function called Garbage Collection ''

Ok, do all SSD drives have that? I am using a Kingston ssd, not a Crucial one “

Respectfully - are we ( you ) adjusting their original position on this issue ?

https://media.kingston.com/support/downloads/secure-erase-user-guide_ksm.pdf

You verify whether any data is still stored on the external SSD by first retrieving the device identifier for the physical external drive. You can get this from Disk Utility. It will be in the form of "diskX" where "X" will be a number. Use the following Terminal command, but make sure to replace "diskX" with the correct device identifier for your external SSD:

First you may need to unmount all volumes on that external drive:

diskutil  unmountDisk  diskX

Second, this will show you the raw data on the specified drive:

sudo  hexdump  -C  /dev/diskX

The second command will prompt you for your admin password. Nothing will appear on the screen as you type the password, so press the "Return" key to submit the password.

Also, the output of the second command will scroll by extremely quickly, but most of it should be zeroes or at least the same value. Sometimes these apps will just stop scrolling and show the last line with all zeroes. Pressing Control + S will pause the scrolling, while pressing most any other key will resume scrolling. Because the macOS Disk Utility "Erase" feature always creates a partition & file system, you may see a few small bits of data mostly at the beginning of the drive/output. If you want to have it go by slowly, then just add " | less" to the end of the command which will allow you to scroll through the output (use Fn + Down Arrow to scroll down by a page/screen)....make the Terminal window to fit the height of the screen in order to view the most data possible for each screen/page full.

sudo  hexdump  -C  /dev/diskX  |  less

If for some reason you don't have "hexdump" installed, then you can use "xxd" instead to get the same output (you can add " | less" to this command as well):

sudo  xxd  /dev/diskX

If you have TRIM enabled & working on the external SSD, then even a simple erase using Disk Utility will be enough to destroy all data on the SSD. I'm not sure when TRIM is not enabled, but eventually it will be zeroed as the others have mentioned with the SSD's Garbage Collection. To enable TRIM for third party SSDs, you can use the following Terminal command:

sudo  trimforce  enable

You may need to run Disk Utility First Aid scan on the external drive volume in order to force a TRIM event to occur right away assuming macOS & the SSD will allow TRIM to be enabled. You can check the Apple System Profiler to see if TRIM is shown as enabled for the specific drive.

Some SSD manufacturers include an option to perform a hardware secure erase using the SSD manufacturer's proprietary software. They may not make a macOS version of the software, so you may need a Windows system.

Of course the simplest option would be to encrypt the external SSD, then erase it destroying the encryption keys.

You are welcome just the same

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