A third advantage of SATA is hotplugging.

A third advantage of SATA is hotplugging.
Currently, SATA has a transfer rate of 150 MB/s, which is only 17 MB/s more than standard PATA.
However, with the introduction of SATA II, this is expected to go up to 300 MB/s, with 600 MB/s
being released sometime around 2007. The faster bus isn't expected to affect performance in the
short term, since hard drive performance is usually bottlenecked by the moving parts of the drive.
During the transitional period before true native SATA drives are released, most SATA drives
actually have onboard PATA controllers, which connect to SATA by a bridge. This generally
causes a 30-50% performance drop. Also, PATA power connectors are still being used.
DMA
DMA (Direct Memory Access) is a function of the memory bus in the computer that lets
connected devices like hard disks transfer data to the memory without the intervention of the CPU,
thus speeding up the transfer. This is superior to the way PIO works.
There are two distinct types of direct memory access, DMA and bus mastering DMA. The plain
DMA relies on the DMA controller on the motherboard to grab the system bus and transfer the
data. In bus mastering DMA all this is done by the logic on the interface card itself. Bus mastering
allows the hard disk and memory to work without relying on the old DMA controller built into the
system, or needing any support from the CPU.
USB
USB (Universal Serial Bus) is a hardware bus using a serial protocol used by many different
hardware devices and supported in most computers/mainboards. Originally developed by Compaq,
Intel, NEC and Microsoft. It allows many devices to be connected to the bus at the same time, the
theoretical maxmium is 127 devices. The maximum data transfer bandwidth is about 12Mbit/s
(USB2.0 supports 480 Mbit/sec).
Firewire is a less known alternative to USB that (at its time) was better then USB for media
related tasks. As of USB2 there have been significant increases, specifically more bandwidth.
SCSI
SCSI - Small Computer System Interface. Pronounced "scuzzy". It's a specification for a hardware
interface for connecting devices such as hard disks and scanners to a computer.
Most PCs have an ATA(IDE) bus instead of SCSI for connecting internal hard disks. SCSI is seen
more often in servers, as it tends to be faster and more reliable (though more expensive). Another
advantage of SCSI controller is that it requires only one IRQ and can hadle usually at least 7
devices whereas ATA can handle only 2.
Typically, you put a SCSI card in your computer, and then connect internal hard disks with a
ribbon cable to some connector on the card. Also, the card will have an external connector which
you might also be using simultaneously.