Most people know that it’s a good idea to buy an external hard drive in order to keep a backup copy of all their important work files. However, ordinary hard drives are still subject to occasional failures, and in the past many businesses and professional users have invested in more expensive RAID storage systems that provide additional protection for their data.

RAID stands for ‘redundant array of independent drives’, which simply means that a RAID drive can hold an ‘array’ of two or more separate hard disk drives. A RAID drive can work in a number of different modes, with each mode providing different levels of performance and data protection. The simplest option for using a RAID drive is known as JBOD – ‘just a bunch of disks’ – which means your computer treats each disk drive as a separate unit. So a RAID drive that contains two separate 1TB disks would show up on your Mac desktop as two separate disks.

Strictly speaking, though, JBOD doesn’t actually count as true RAID storage, as the two hard disks aren’t linked in any way – they’re treated as two completely separate disks. The first true RAID mode is known as RAID 0. This mode treats those two 1TB drives as a single 2TB drive. However, when you copy a file onto the RAID drive, that file is split into smaller chunks, and those chunks are then spread – or ‘striped’ – across both hard disks at the same time. This provides better performance than a conventional hard disk as you’re copying data onto two drives at once (or even four if your RAID drive contains four drives).

A RAID 0 storage system can be useful for people such as photographers or video editors who need a fast hard drive for working with very large photos or video files. They’re particularly handy for Photoshop users, because of Photoshop’s intensive use of hard disk space – known as a ‘scratch disk’ – when handling very large files.

But while RAID 0 does provide improved performance, it doesn’t offer any extra protection for your important files. If one of the drives breaks down then your data may still be lost. You can trade some of that performance for additional reliability by using RAID 1 mode as an alternative.

A drive configured in RAID 1 mode will store separate copies of your files on each hard disk (a process known as ‘mirroring’ as each hard disk is an identical mirror image of the other). You lose some of the storage space – your two 1TB drives will appear to act like a single 1TB drive instead – but if one drive fails you will still have the mirrored copy of your files kept safe on the other drive.

Using multiple hard disk drives obviously means that RAID drives are more expensive than conventional hard drives, but the low cost of storage these days has given rise to a new generation of RAID drives that are affordable enough even for self-employed and home users. So here’s a round-up of some of the latest RAID drives available for Mac users.

Buying Advice

There’s no single product in this group that will meet the needs of all Mac users. A RAID system that protects the work of a self-employed photographer might not be suitable for larger corporate or educational users. It’s therefore important to identify the product that provides the specific features you know you’ll require for your own work.

Thankfully, performance isn’t really an issue, as most of the drives here provide similar performance levels – the only major exceptions being the G-Safe drive, which doesn’t have a fast RAID 0 option, and the Verbatim 2 Disk drive, which lacks the FireWire interface that many Mac users prefer.

However, if you’re on a tight budget the 2 Disk provides a healthy 2TB of storage at an affordable price. And while it doesn’t have FireWire it does have both USB 2.0 and eSATA interfaces, which means that it’s still a good option for Mac Pro or MacBook Pro users who need the speed of eSATA.

At the other extreme is LaCie’s 4Big drive. This is the most expensive drive in the group, coming in at over £600 with 2TB capacity, but its four-drive design allows it to provide additional RAID options that aren’t available to the other drives with only two hard disks. This is the only drive in the group to provide RAID 6, which keeps one drive completely free so that it’s available as an emergency backup if one of the other drives fails. That will certainly appeal to business users who need rock-solid reliability from their storage systems.

Another extremely reliable – and slightly more affordable – option is the G-Safe drive from G-Tech. At more than £400, it’s still relatively expensive, but its rugged metal casing provides plenty of physical protection, while the hot-swappable drive bays ensure that you can quickly replace a faulty drive or keep a spare backup drive in another location for extra security. This is probably the best option for small businesses and self-employed individuals, such as photographers, who want to keep their digital assets as safe as possible.

Another drive that provides additional security options is the Freecom Data Tank. The ability to encrypt the drive so that people can only gain access to your files with a password will appeal to many business users. However, for all-round value for money, ease of use and Mac-compatibility, Western Digital’s My Book Studio Edition II proves hard to beat. It provides 1TB of storage at a very good price, includes every major interface option, and Western Digital’s well-designed Mac software pays good attention to detail with handy options such as the capacity gauge that shows you instantly how much room you have left available.