some ZFS questions

Michael Sierchio kudzu at
Mon Aug 25 20:25:40 UTC 2014

On Mon, Aug 25, 2014 at 11:24 AM, Roland Smith <rsmith at> wrote:

> With modern drives the data density is so high that it is almost impossible to
> retrieve single overwritten bits, let alone bytes or files if the complete
> disks was filled with zeroes.

That is unfortunately naive - all modern drives, whether spinning
platters or SSDs, silently remap sectors when they detect incipient
errors, for wear leveling in the case of SSDs, etc.  This means that
it is possible for someone with direct access to the disk to recover
whole sectors - sectors that you cannot erase, no matter how many
synchronous writes you perform in the OS.

- M

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