It's pretty uncommon for technically inclined folks to just abandon a disk with unencrypted data.
And from what I remember reading long ago, several writes of random data is more secure than several (or one) writes of zeros.
And from what I remember reading long ago, several writes of random data is more secure than several (or one) writes of zeros.
AFAIK for a recent (say, 2010 and later) drive - there's little to indicate random/"smart" patterns are better than just a single pass off all zeroes. Even if you consider an adversary with the capability to analyze drive with magnetic force microscopy.
https://www.howtogeek.com/115573/htg-explains-why-you-only-h...
https://www.sans.org/blog/overwriting-hard-drive-data/
"Data Reconstruction from a Hard Disk Drive using Magnetic Force Microscopy", 2013 Author(s): Kanekal, Vasu https://escholarship.org/uc/item/26g4p84b
A quick skims seems to indicate the NSA recommends degaussuing and destruction: https://www.nsa.gov/resources/everyone/media-destruction/
Nist 800-80: https://www.nist.gov/publications/guidelines-media-sanitizat...
Refers to: https://cmrr.ucsd.edu/resources/secure-erase.html
Who's readme: https://cmrr.ucsd.edu/_files/hdd-erase-readme.txt
And q'n'a indicate that single pass sata secure erase is generally considered sufficient - it typically does a single pass, but should also write over all bad blocks etc.
See also: https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase
It's even worse with SSD drives, where the "hidden reserve" many times larger.
Wiping is of course better than doing nothing, but neither lives up to the requirements of GDPR.
Where wiping disks is sufficient, for instance "internal reuse", it is always some number of specified writes, followed by writing all zeros, so both the donor and receiver can verify the disk as empty.
Note that wiping a SSD with all-zeros is likely to be optimized out by its embedded controller.