The WD20EARS, along with the companion 1TB WD10EARS, are the first 3.5" drives to hit the market with Western Digital's new formatting structure, which divides the drive into 4,096-byte sectors instead of the smaller 512-byte sectors used in current drive technology.

The advantage? Fewer, larger sectors mean less drive space devoted to lead-ins and inter-sector gaps, which allows for formatting efficiencies in the high-90% range and usable-space increases of more than 10%. In short, it's a way to get more actual storage space from the same physical drive.

While larger sectors make sense for battling the diminishing returns on usable space as drives grow in size, it's worth noting that not all operating systems support this new technology. Windows users (including WHS users) from Vista forward should have no trouble, and the latest versions of Mac OS X and Linux are reported to handle 4K sectors without third-party software. If you're running XP, however, be aware that you'll have to use a software solution (WD's supplied WD Align tool, which provides 512-byte emulation) to get optimal performance, and you'll have to be even more creative in patching together a workable solution if you happen to use Windows Home Server 2003.