System Recovery

Ben Scott dragonhawk at gmail.com
Tue Jul 15 23:27:43 EDT 2008


On 7/15/08, Jim Kuzdrall <gnhlug at intrel.com> wrote:
>    Curious.  Why not use the non-destructive badblocks write option -n?

  Background: The "non-destructive write test" goes through the disk,
one block at a time, reading the existing contents into memory, then
writing and reading test patterns on that block, then writing out the
saved contents again.  The "destructive write test" writes a test
pattern to every block on the disk, then reads/compares, then repeats
for each successive test pattern.

  So, my reasoning: First, the extra I/O to preserve the existing
contents slows things down significantly.  If you're wiping the disk
anyway that's a waste of time.  Second, because the destructive test
writes the pattern to the entire disk before reading anything, if
there's anything weird going on with caching or bleed-over or whatever
horror story you can dream up, it's more likely to flush it out.
Finally, the destructive test leaves every block on the disk zeroed,
which clears out any residual traces of anything that might confuse
the installer during the reinstall.

-- Ben


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