The easiest way to obtain hard drive's model information is to use smartmontools and its smartctl command. If you do not have smartmontools package installed on your system yet you can do so by:
# apt-get install smartmontools
# yum install smartmontools

Once the installation is done and smartctl command available run do following command to retrieve your hard drive's model information. In the example below we use /dev/sda as block device.
# smartctl -a /dev/sda | grep Model
Model Family:     Hitachi Travelstar 7K100
Device Model:     HTS721060G9SA00