Western Digital has quietly updated its MyBook and MyBook Duo Thunderbolt external storage solution with 4TB and 8TB models, respectively. The former is the world's highest-capacity external hard disk drive with Thunderbolt interface, which can be configured for maximum performance, maximum security or maximum capacity.

From now on, WD offers My Book Essential external hard drives with 1TB, 2TB, 3TB and 4TB capacities and with USB 2.0 and SuperSpeed USB 3.0 storage. It is believed that the hard drives that Western Digital uses for its external My Book Essential storage solutions have 5400rpm rotating speed. WD My Book Essential costs $209, whereas 3TB, 2TB and 1TB models are priced at $159, $129, and $109, respectively.

Besides, in addition to 4TB and 6TB models, the My Book Duo Thunderbolt family of external hard drives now includes a 8TB model. WD My Book Thunderbolt Duo external dual-drive storage systems are based on two 2TB, 3TB or 4TB hard disk drives, RAID controller, Thunderbolt controller and other logic needed to provide professional-grade functionality. The drive serves as a safe and reliable way to backup content stored on computer while providing the fastest way to get information to and from the WD drive thanks to 10Gb/s interface. The RAID 1 allows users to create a second copy of their digital content on the drive for double-safe protection, RAID 0 allows to boost performance of the storage sub-system and the JBOD mode to allocate each disk individually to a specific task.

WD does not indicate which hard disk drives (HDDs) it used inside the My Book Thunderbolt Duo. Some sources indicate that WD installs two drives with 7200rpm spindle speed, but WD does not have a 3TB HDDs with 7200rpm spindle speed in its lineup now, therefore, the company either utilizes unannounced hard drives, HDDs made by HGST or simply installs HDDs with 5400rpm spindle speed. Performance testing by WD resulted in an average actual transfer rate for Thunderbolt of  over 250MB/s on 6TB systems and 225MB/s on 4TB systems.

The My Book Thunderbolt Duo is available now starting at $559.99 for 4 TB model, $659.99 for 6 TB model and $849.99 for 8TB model.

Tags: WD, Thunderbolt, My Book, HDD, Western Digital