The biggest speed bottleneck is likely to be the physical interface to the disk, as anyone whos tried using USB 1.0/1.1, and then gone to USB 2 ("Hi-Speed") or to FireWire.(IEEE 1394), knows.
SATA (Serial Advanced Technology Architecture), which can do data rates up to 3G bps, is rapidly supplanting the older ATA (aka Parallel ATA, PATA), which has been around since the 1980s, for internal drives in desktops, notebooks, NAS devices and smaller or low-cost servers—and now, also in external hard drives.
This lets Seagates eSATA Pushbutton Backup Hard Drive—now available in 300GB and 500GB versions—move data up to five times faster than your USB 2.0 or Firewire external hard drives.
Of course, your computer needs to have a SATA port to do this. If your computer doesnt already have one, but has room for a PCI card, you can install the two-port Promise Technologies PCI-to-SATA host adapter card thats included in the Seagate eSATA box (along with drivers and instructions).
If you cant do this, or the PCI card doesnt work, you can use a $30 USB2.0-to-eSATA adapter, such as Coolmaxs ES-300 USB2.0 to eSATA Converter.
Users wont see SATA speeds with the USB adapter, but the adapters are handy if users want to use the eSATA with a notebook or another desktop.