Western Digital has increased the capacity of its My Book Studio Edition II external hard drive to 4TB. Designed to be used with both Macs and PCs, it lets you choose from plenty of different connections and it can be configured for speed or data redundancy.

Coated in a silver finish, the My Book Studio Edition II (4TB) has the same sleek, book-like enclosure that will be familiar to users of any of Western Digital's My Book range of external hard drives. The rounded LED on the front of the enclosure doubles as a capacity and operation indicator. At the back there are two FireWire 800 ports, as well as an eSATA port and a mini-USB 2.0 port. The retail package comes with a FireWire 800 cable, a FireWire 800 to FireWire 400 adapter and a mini-USB to USB cable; an eSATA cable is unfortunately omitted.

The WD My Book Studio Edition II (4TB) external hard drive employs two 2TB Western Digital Caviar Green hard drives in a RAID 0 configuration, which improves read and write speeds. The internal hard drives are cool and quiet, so the My Book Studio Edition II (4TB) itself is silent during operation. The enclosure is passively cooled through perforations along the top and back of the casing and rarely gets warm.

Out of the box the My Book Studio Edition II (4TB) external hard drive is formatted with the HFS file system, so it can be used with Mac computers; Windows users will have to format it to NTFS or use an application like MacDrive to get it working. The My Book Studio Edition II (4TB) is Time Machine–friendly, so it's dead easy to set up automatic backups for your Mac computer through Mac OS X.

For PC users, Western Digital has provided its Anywhere Backup and Memeo AutoSync applications to automatically back up and sync information and folders. A Mac version of Anywhere Backup is available but it isn't as useful or intuitive to use as Time Machine.

There is also a 30-day, PC-only trial for MioNet, Western Digital's remote access interface for its hard drives.

Using Western Digital's Drive Manager on either a PC or a Mac you can alter the drive configuration to a RAID 1 array, which decreases overall performance and halves capacity but provides increased data security; data is mirrored on the MyBook's two drives.

Should one of the internal hard drives fail, replacing it is fairly simple. The case's top opens and after unscrewing the metal bracket you can use plastic handles to extract the hard drives. The My Book Studio Edition II (4TB) external hard drive will support any Western Digital internal hard drive; other brands aren't compatible.

We tested the external hard drive by transferring data between it and a 300GB Western Digital Velociraptor. Over eSATA, the external hard drive wrote 20GB worth of 3-4GB files at a rate of 77.3 megabytes per second (MBps), read them at 89.4MBps and performed a simultaneous read/write operation at 41.9MBps. It wrote 3GB of 1MB files at 51.7MBps, read them at 54.5MBps, and performed a simultaneous copy transfer operation at 41MBps. FireWire 800 speeds were much the same, though the 3GB small file test was marginally faster.

USB 2.0 speeds were understandably much slower: the My Book Studio Edition II (4TB) external hard drive wrote 20GB of large files at 25.1MBps, read them at 26.7MBps and transferred the same data to another portion of the drive at 12.7MBps. In the small file test, the external hard drive had a write speed of 15MBps, a read speed of 23.4MBps and a simultaneous read/write speed of 10.7MBps. Both the USB 2.0 and eSATA file speeds are much faster than this external hard drive's closest counterpart, the LaCie 4Big Quadra (4TB).

Though the LaCie 4Big Quadra has extensive RAID configuration options and four drive bays, the Western Digital My Book Studio Edition II (4TB) is cheaper and faster.

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