Hdparm is a performance tool for your Hard Disk (SATA/IDE). Be careful, it's easy to destroy your HDD with hdparm!
hdparm is available in base repo. For SCSI devices, take sdparm.
To get information about your Disk, just do
# hdparm -I /dev/sda
Reading speed MB/s
To mess how many MB/s your Hard Disk (IDE/SATA) can rrad.
# hdparm -t --direct /dev/sda
Writing speed MB/s
$ sync;time bash -c "(dd if=/dev/zero of=bf bs=8k count=500000; sync)"
Don't forgett to ctrl+c and rm bf after that.
Parking your HDD
If your HDD is clicking many times, the kernel is parking the reading head of the HDD. This happened often on Laptops (2.5" IDE HDDs). If it happend to often, it could damage your HDD.
This will just parking the reading head when you shutdown.
# hdparm -B254 /dev/sd
Default value is -B128. A average value could be -B199 if it's parking to often.