Where do I save the hdparm command?

[promethus]

/etc/hdparm.conf does not exist and I read from this thread that it does not get sourced. Should I use udev rule instead? I actually do not know what udev rule is. Any pointer, or tutorial would be appreciated, because I am not even sure if it relevant to my distro. Does it have any relationship with udevil?

All I want is my pogoplug to execute:
$this->bbcode_second_pass_code('', 'hdparm -S 120 /dev/sdb1')
whenever I reboot.
Would placing that in .bash_profile suffice?