From: Carl Lowenstein <cdl@mpl.ucsd.edu>

>Is there some confusion here betwen "format" which uses the disk
>firmware to rewrite the sector headers, and "surface check" which
>can overwrite all the existing data?

Who would confuse those two?  A real low-level format that rewrites the
headers, also rewrites the data fields (there's really no way not to,
since the concept of "data field" loses its meaning w/o headers, so the
drive wouldn't be able to guarantee perfect positioning of the new headers
between the old data fields even if it DID want to turn the write head
off between headers), so it's a nice cheesy way to wipe a whole disk w/o
thinking about it too hard (i.e. you don't need an OS, just some crude
firmware that sends one command).

A really "responsible" surface check program ought to restore the original
data anyway after the test is over, so that the test is non-destructive.
So a surface check doesn't *necessarily* wipe the disk.

John Wilson
D Bit