hdparm

Your system should always make sure you have DMA installed, except in this case: http://www.thinkwiki.org/wiki/Problems_with_SATA_and_Linux#No_DMA_on_system_hard_disk I’ve discovered that my internal hard drive (hda) is as fast as my external USB2 hard drive(sda).

monty$ sudo hdparm -Tt /dev/hda

/dev/hda:

Timing cached reads:   858 MB in  2.00 seconds = 428.54 MB/sec

Timing buffered disk reads:   56 MB in  3.07 seconds =  18.27 MB/sec

monty$ sudo hdparm -Tt /dev/sda

/dev/sda:

Timing cached reads:   1040 MB in  2.00 seconds = 520.12 MB/sec

Timing buffered disk reads:   56 MB in  3.05 seconds =  18.33 MB/sec