I want to securely delete the hdd using dd because I intend to sell it. Using the buffer will speed up the process. I can't find out the size though:
arno@arno-X55A:~$ hdparm -i /dev/sdb
/dev/sdb: Permission denied
arno@arno-X55A:~$ sudo hdparm -i /dev/sdb
[sudo] password for arno:
/dev/sdb:
HDIO_GET_IDENTITY failed: Invalid argument