>> On Sun, Nov 16, 2014 at 2:04 PM, jd1008 <jd1008(a)gmail.com
>> <mailto:jd1008@gmail.com>> wrote:
>>
>> Before sending the drive for warranty service, what is the best
>> way to clean the unallocated blocks?
If this is really important to you, just eat the cost of the drive and
destroy it instead of sending it back.
If not modern drives provide a secure erase function and you should use
that. You can use hdparm to do this.