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With an HDD, your operating system can (mostly) directly access bits on the magnetic disks, so you can wipe them by just writing 0 to it over and over (historically, there was a paper saying 7 times would make any bits unrecoverable - this changed as density got higher)
With SSDs, your operating system has very little control over what bits a write is touching, a lot more was moved into the firmware on the flash memory itself
So SSDs need a special command “Secure Erase” to wipe them
Yeah, and as densities have increased, fewer passes have been needed to even do that