with data caching).Īnother method for secure erasure, which is quite more efficient, is encryption: Disks in the wild have been known to take some liberties with the specification at times (e.g. From the ATA specification point of view, there are two commands, and there is no real way to know how the erasure is implemented, or even whether it is actually implemented. one of the spare sectors is used by the disk firmware when the computer reads or writes it). It also overwrites sectors which are no longer used because they triggered an I/O error at some point, and were remapped (i.e. It overwrites data several times with distinct bit patterns, to be sure that the data is thoroughly destroyed (whether this is really needed is subject to debate, but there is a lot of tradition at work here).
The "enhanced secure erase" tries harder: On such a disk, at any time, there is a logical view of the disk as a huge sequence of numbered sectors the "secure erase" is about overwriting all these sectors (and only these sectors) once, with zeros. This sentence makes sense only for spinning disks, and without encryption. Enhanced secure erase writes predetermined data patterns (set by the manufacturer) to all user data areas, including sectors that are no longer in use due to reallocation. Secure erase overwrites all user data areas with binary zeroes.
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