I have a disk with enough unreadable portions that it's being replaced 
under warranty by the vendor.  I would like to overwrite whatever 
portions of the disk I can.  Trying to do that in a straight-forward 
fashion runs afoul of the error recovery code; it slows down the 
attempt or even prevents it.  Any suggestions on what to do?  (This is 
an SATA disk on -current/i386.)

		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb