[buug] best way to dd lots of drives (ide, scsi, etc)

Michael Paoli Michael.Paoli at cal.berkeley.edu
Tue Sep 8 19:33:57 PDT 2009

"best", "dd" and "data destruction" don't all correlate 100%,
so there are tradeoffs, depending upon one's objectives - but
more precise criteria wasn't specified.

If you simply want a one pass overwrite of reasonably accessible data
at maximum speed:
o be sure any BIOS setting or the like which make any part of the disk
   "hidden" are disabled (tends to be a more common issue for laptops and
   "desktop" type systems).
o determine optimal (or near optimal) block size and device (e.g. block
   vs. character device - if applicable for your OS flavor) - once you
   figure that out it typically won't vary much across drive types - at
   least if you're using similar hardware to do the overwrite/"wipe".
o # dd if=/dev/zero of=/dev/highest_throughput_disk_path \
   > bs=highest_throughput_block_size
o If your OS flavor doesn't provide /dev/zero, one can use a wee bit of
   code (e.g. C or perl) to produce an infinite output of ASCII null
   bytes, and pipe (|) that into dd (and omit the if=/dev/zero).
o These can be done in parallel (asynchronous &) - but if one does so,
   one may want to take proper care to capture exit/return value and any
   data written to stderr
o The above method is relatively fast, and leaves the drives useable
   (e.g. for resale or donation, etc.).
o Rather than being too redundant, continue with further information
   (same basic stuff applies - essential tradeoffs are thoroughness,
   time, reusability, convenience, risk/security, etc.)

Quoting "Bob Read" <unixjavabob at yahoo.com>:

>   file under:  data destruction.
>   I need to dd a whole bunch of drives ( ~20/month) of different
> types (ide, scsi).
>   whats the best way to dd them all?
>   they're sitting in a stack in the corner.

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