4 ms·

/dev/urandom is far better option. One problem is that writing a full drive of data can take long time vs chucking it into shredder. For example this[1] 22TB dr

by zokier 3y ago

/dev/urandom is far better option. One problem is that writing a full drive of data can take long time vs chucking it into shredder. For example this[1] 22TB drive can do 260MB/s, meaning that doing one full disk write pass would take almost 24h. [1] https://nascompares.com/2022/09/12/wd-red-pro-22tb-hard-drive-review-wd221kfgx/ https://nascompares.com/2022/09/12/wd-red-pro-22tb-hard-driv...

Gordonjcp 3y ago
In the olden days hard disks wrote data on spinning platters the size of dinner plates with heads the size of Sharpie markers, and the controllers were a Z80 microprocessor on a card with a few kB of ROM and maybe as much as 16kB of RAM. Everything past those days though, the data is very thoroughly scrambled for spectral whitening before being written to disk so there's no practical difference between /dev/urandom and /dev/zero.
charcircuit 3y ago
What makes it far better? When overwriting a full drive they are about the same.
- pessimizer 3y ago
  Intuitively because if you're just writing zero bytes everywhere, and there's a lab that can detect the difference between a zero that used to be a one and a zero that was always a zero, they can get the entire drive. When I get a drive, I LUKS encrypt it and fill it with zeros before throwing a filesystem on it, which results in the drive looking entirely like random nothing. The privacy test that it definitely fails is that disks don't ever look like that unless they're encrypted, but I'm not worried about anybody finding old drives.
  - Bedon292 3y ago
    My current understanding is that it is no longer possible to detect those differences on modern drives. I believe it has come down to density. Where it was possible when density was much lower, and you could detect some residual information from the wide tracks. But things are so dense now those residuals aren't physically possible.
  - Gordonjcp 3y ago
    > there's a lab that can detect the difference between a zero that used to be a one and a zero that was always a zero No, there isn't, and hard disks haven't worked that way since before Windows existed.

by zokier 3y ago

Gordonjcp 3y ago

In the olden days hard disks wrote data on spinning platters the size of dinner plates with heads the size of Sharpie markers, and the controllers were a Z80 microprocessor on a card with a few kB of ROM and maybe as much as 16kB of RAM. Everything past those days though, the data is very thoroughly scrambled for spectral whitening before being written to disk so there's no practical difference between /dev/urandom and /dev/zero.

charcircuit 3y ago

What makes it far better? When overwriting a full drive they are about the same.

pessimizer 3y ago
Intuitively because if you're just writing zero bytes everywhere, and there's a lab that can detect the difference between a zero that used to be a one and a zero that was always a zero, they can get the entire drive. When I get a drive, I LUKS encrypt it and fill it with zeros before throwing a filesystem on it, which results in the drive looking entirely like random nothing. The privacy test that it definitely fails is that disks don't ever look like that unless they're encrypted, but I'm not worried about anybody finding old drives.
- Bedon292 3y ago
  My current understanding is that it is no longer possible to detect those differences on modern drives. I believe it has come down to density. Where it was possible when density was much lower, and you could detect some residual information from the wide tracks. But things are so dense now those residuals aren't physically possible.
- Gordonjcp 3y ago
  > there's a lab that can detect the difference between a zero that used to be a one and a zero that was always a zero No, there isn't, and hard disks haven't worked that way since before Windows existed.