External Serial ATA, or eSATA for short, is a great alternative to USB for speedy external storage devices. Performance is theoretically the same as with an internal hard drive, and any machine can turn a free internal SATA port into an external one (although this approach does reduce the maximum supported cable length). However, eSATA presents a disadvantage for smaller storage devices because it requires an external power supply. This shortcoming is exemplified by some awkwardly-designed eSATA flash drives that use an eSATA connection for data and an auxiliary USB connection for power.
To get around this problem, the Serial ATA International Organization—the consortium behind the SATA standard—has decided to create an updated eSATA specification (PDF) that removes the need for external power connections. Known as Power Over eSATA, the specification will be backward-compatible with existing eSATA hardware, but it will allow a host system to supply power to an external device straight through the eSATA cable.
According to SATA-IO, the Power Over eSATA specification is set to be completed some time in the second half of 2008, and the first devices based on the new standard will become available in roughly the same time frame. The new spec will presumably pave the way for smaller and leaner eSATA devices.