There are various options to connect external disc space to your PC/MAC but for larger data amounts – raster data or HD footage – you will likely try to use some of the faster options avail.
As I invested into G-Drive harddiscs for satellite image data storage I have all fast interfaces already installed and a test of the connection speed was easily done. To get eSATA working all I had to do was to buy a 20€ ExpressCard eSATA controller for my MacBook Pro and thats it.
Xbench gives some very nice figures when you compare the read write statistics using different standards. It boils down to the following numbers (all these are uncached (256k Block) write/read values in MByte/s):
The internal SSD drive is the fastest – no suprise, but eSATA is a bit on the weak side suprisingly but about at the max of what G-Drive HDs are specified for with eSATA. The theoretical write speed for eSATA: 300 Mbyte/s, FireWire800 (ieee 1394b): 100 Mbyte/s, USB2: 40 Mbyte/s max).