The My Book World Edition II looks similar to other My Book external hard drives we've seen. This NAS device runs almost silently. It does not have any fans installed; instead it's cooled passively through perforations in the enclosure. The drives in the My Book World Edition II are not hot-swappable, but they can be replaced should they ever fail. However, only Western Digital's 3.5in Caviar Green SATA 2 internal hard drives are recognised by the device.
The My Book World Edition II has Gigabit Ethernet and USB ports. The USB port can be used to attach an external hard drive, so you can add more storage space or back up data on the NAS. Unfortunately, it can't be used to attach a printer.
Western Digital provides basic backup software with the My Book World Edition II 4TB as well as its proprietary remote access service, MioNet. Using either the supplied software or MioNet's website, you can remotely access your Western Digital NAS devices and external hard drives, and also publicly share folders with other MioNet account users. Unlike Apple's MobileMe service, you can't configure a publicly shared folder for non-Mionet users. MioNet software support is currently limited to 32-bit Windows machines. A premium account, which adds remote desktop and remote access features, attracts a subscription fee.
The MyBook World Edition II can be configured through its web interface, which has Basic and Advanced modes. Using the interface you can alter user access and quota settings, as well as update the device's firmware. Like Western Digital's Sharespace range, you can configure the two 2TB Caviar Green hard drives in a RAID 0 array for speed or RAID 1 for data redundancy. You can also use JBOD, which configures the drive separately, or Span, which combines the drives' capacities without RAID capabilities. The device is set to RAID 1 by default.
The My Book World Edition II can be accessed from computers running Windows, Mac OS X and Linux, and it can be used as a Web and FTP server. It also includes an iTunes server and a Twonky-powered UPnP server, so you can stream media to computers and DLNA devices on your network.
Western Digital's Caviar Green hard drives allow the MyBook World Edition II 4TB to consume less power than other NAS devices we have tested. During our tests, it consumed 16.6 Watts when idle, which is significantly less than the 23W used by the QNAP TS-219 Turbo NAS (with two Seagate Barracuda 7200.11 1.5TB hard drives).
Connected via Gigabit Ethernet to our testbed (which has a Western Digital Velociraptor (WD3000GLFS)), the My Book World Edition II 4TB NAS device wrote 20GB worth of 3-4GB files at a rate of 14.4 megabytes per second (MBps). It read the same data at a rate of 35.5MBps and performed a simultaneous read/write operation at 9.1MBps. In our small file transfer test, which uses 3GB of 1MB files, the NAS device's write speed was 7.2MBps, its read speed was 14.6MBps and its read/write speed was 4.3MBps. Though its read speeds are adequate, overall this NAS device is significantly slower than other two-bay NAS devices like the QNAP TS-219 Turbo NAS. We achieved similar speeds using both RAID 0 and RAID 1 configurations.
When testing with the Intel NAS Performance Toolkit synthetic benchmark the results of the My Book World Edition II 4TB were adequate. It streamed 720p HD footage at an average rate of 37.8MBps and it performed simultaneous read and write tasks at 28.5MBps. It recorded 720p footage at a rate of 13.6MBps, which is a slow result.
Despite comparatively slow performance, the My Book World Edition II 4TB's ease of use, large storage capacity, RAID functions and reasonable price make it a decent entry-level NAS device.
Western Digital's 4TB My Book World Edition II NAS device is an easy and reasonably cheap way to store large amounts of data in a central location. Its overall performance is slow, but for tasks where speed isn't critical this NAS device is a decent choice.