The number of announcements by hard drive manufacturers says it all: the trend is moving towards 2.5" models. Models with 5,400 rpm are nothing special anymore; Hitachi even has the first notebook drive with 7,200 rpm ready to go. However, it should be set up for long-term use and should not consume significantly more power than models with lower rpms.
The smaller disks used to reach rotation speeds like that take less power. There is even considerably less heat generated in the process, thanks to the smaller frictional surface. The durability of such hard drives should be better, since the mechanical strain on the components is lower. Because of this, it is possible to use them in server systems that do not need to supply very large quantities of data (e.g. Web servers).
In one respect, the movement away from 3.5" and towards 2.5" makes for a considerable disadvantage: considerably lessened performance. Even if caches with 8 MB soon gain acceptance with notebook drives, the absolute speed of magnetic disks is lower and, thus, the data transfer rates lag behind. For desktop use, therefore, that means cutting corners.
However, in terms of mobility and saved space, the coming 2.5" generation is a leap ahead. They are connected as usual via UltraATA (host adapters are available in stores); even serial ATA is already possible . Use in external storage systems is only logical, because no other media currently stores data sets of up to 80 GB in such a small space.
Power Supply Via FireWire Or USB
None of the three candidates come with a power supply, because, according to the manufacturers, power is supplied to each of the three via its respective interface. With the USB versions, this worked absolutely flawlessly, as long as a current 2.0 standard USB 2.0 controller was used. The Fujitsu HandyDrive (Data Edition) was not recognized by a system with an Intel Southbridge ICH2 and USB 1.1; same thing for the Video Edition with an old Sony Vaio notebook with FireWire. Tests with a recent Samsung Q10 and a PCI-based FireWire controller ran without a problem.
Things get more critical with FireWire when several devices are strung along, one after the other. In this case, the HandyDrive could not be operated without help from a separate power supply; the load on the FireWire was too heavy.