WD is busily upgrading MyBook editions - hot on the heels of the 4TB Studio Edition II comes the World Edition II with doubled capacity of 4TB, courtesy of two 2TB drives, and sharing the SE II enclosure.

The WE II is for shared file storage and networked computer backup in the home. Its small business equivalent being the ShareSpace. It has gigabit Ethernet connectivity and supports both Windows and Mac computers in the home.

The WE II's pair of hard drives can be configured in RAID 1 mirrored form for protection against a drive failure, obviously halving the raw capacity, or RAID 0 striped form for capacity. It includes software that helps users set up automatic and continuous data backup for all the PCs in the home.

As before the WE II can serve digital media files to DLNA-compliant devices and iTunes servers. Users can also access their WE II-stored files from anywhere in the world through the internet using the included and free MioNet remote access service.

There is lots of competition in this home network-attached storage (NAS), backup and media file serving area, for example from the LaCie 2big Network model, which looks like a blue cyclops-eyed white box instead of a plastic imitation of a book. Buffalo, Cisco, Drobo, Iomega and Seagate also have products in this area.

A 4TB WE II is $700 (£600) and a 2TB one is $400 (£370). ®