The only other drive on test that supported hardware configuration was the LaCie 2big Quadra. That has inset switches on the back and comes with a special tool that allows you to press them. However, it is a little fiddly, and you need to make sure you read the instructions particularly carefully beforehand.
Of the others, the WD and Buffalo have proprietary RAID management tools, while both the Thunderbolt drives rely on OS X's Disk Utility in order to change the RAID settings. That's okay, but Disk Utility is not the friendliest tool to use. LaCie provides some detailed instructions, whereas G-Tech simply points you to Apple's support website.
Test three: Extra features
Little extras can make all the difference
The Buffalo and LaCie 2big USB 3 both have USB 3 connectors. While only the most recent Macs support this version of USB, it offers significant speed improvements over USB 2 and FireWire 800.
Both LaCie drives also come with Intego Back Up Manager Pro, while the WD My Studio II has a proprietary set of software tools on CD. The My Book Studio II also has a useful capacity gauge on the front and offers USB 2, FireWire 800, and eSATA connectors.
The G-Tech G-Raid has the same connectors as the My Book Studio II and includes a FireWire 800 to FireWire 400 cable in the box, as well as a standard FireWire 800 cable; useful if you have an older Mac or want to daisy-chain older FireWire peripherals.
The CRU-DataPort also has a FireWire 800 to 400 cable, and includes a copy of ProSoft's Data Backup. LaCie deserve special praise for including a Thunderbolt cable in the box with its drive. There's no cable with the G-Tech G-Raid with Thunderbolt. A narrow win for the My Book Studio Pro II in this test.
Test four: The drives in use
How do the drives perform day-to-day?
Once you've set up your RAID drive and scheduled backups, you should be able to forget it. But there are a couple of issues worth considering.
The first is heat generation. These drives may well be running 24/7 so reducing the amount of heat they produce is important. The My Book Studio is the only drive on test that doesn't have a fan, relying instead on a 'chimney' convection cooling system.
The Buffalo, CRU-DataPort and G-Tech units all have fans that blow air out the back. But the LaCie drives have fans and a chassis designed to dissipate heat, in the same way as a CPU heatsink does. Also, the Buffalo is very noisy in use.
The other issue is the ease with which a drive can be replaced; the point of RAID 1 is redundancy. The G-Tech doesn't offer that at all, and while the WD does, it's fiddly. The Buffalo is better, while both the LaCie and CRU-DataPort have lever-based systems for sliding drives out without opening the case. The CRU-DataPort offers extra security, allowing you to lock the bays.
The winner: Lacie 2Big Quadra 4TB
Choosing a back-up destination is one of those rare occasions when the differences in price between the drives on test is relatively unimportant. Will you care that you saved yourself £50 if the drive you buy fails when you need it most?
Nevertheless, the price of the CRU-DataPort drive compared to the other non-Thunderbolt drives is just too high to name it as winner. Likewise, neither Thunderbolt drive offers enough to justify the premium price.
Of the three that are left, two have plastic cases making them less robust than their metal-enclosed competitors. For that reason, along with the ease with which failed disks can be replaced, and the inclusion of USB 3 and FireWire 800, the LaCie 2big Quadra USB 3 is our winner this time around.