In an announcement that marks the gradual expansion of the USB 3.0 devices' band, Western Digital has added two new My Book 3.0 external hard drives - a 1TB storage version and a 2TB storage version.

The 1TB My Book 3.0 version is available for sale as a standalone component for $179.99; and costs $199.99 when packaged with a PCIe USB 3.0 adapter card. Meanwhile, the 2TB My Book 3.0 version will be introduced next week, and will cost $279.99.

Going by the results of the PC World Lab tests, USB 3.0's maximum performance of 4.8 Gbps is theoretically ten times better than the 480 Mbps performance of USB 2.0. However, in real-world situations, the bottlenecks in the USB 3.0 environment lead to only a three times' increased performance of the drive over its USB 2.0 counterpart.

Tests with the drive's adapter card showed that the My Book 3.0 could read a 3.7GB folder in only 40 seconds; as against the 133 seconds clocked by the USB 2.0 to read the same folder.

Furthermore, USB 3.0 took 53 seconds to write that folder of files, while USB 2.0 took 151 seconds to write the same folder of files.

In terms of reading and writing a single 3.7GB file, USB 3.0 sailed through the tests taking 28 seconds and 34 seconds respectively; while USB 2.0 took 122 seconds and 127 seconds respectively.