If you want to find additional information on your hard disks in linux you can use an utility called: hdparm.
If you can’t find this utility install it using apt-get on debian: apt-get install hdparm
then at the console type: hdparm -I /dev/sda an it should list something like this:
/dev/sda:
ATA device, with non-removable media
Model Number:       ST31000340NS
Serial Number:      [...]