Multi-drive devices use RAID (Redundant Array of Inexpensive Disks) technology to provide faster performance, security in case of drive failure, or both. Most devices offer a choice of RAID settings, which are altered either using supplied software or switches on the back of the unit. RAID has a reputation for being impenetratably techie – which is why manufacturers use terms and settings such as ‘Fast’ (or ‘Large’) and ‘Safe’ instead of RAID 0 or RAID 1 – but for desktop storage, it’s simple.
The most straightforward form of RAID is called JBOD – which is an acronym of Just a Bunch Of Disks, and is exactly that. Drives are combined into a single volume – so it appears as a single drive in the Mac OS X Finder or Windows Explorer – and data is written to the first drive and then, when that’s full, to the next – and so on.
RAID 0 also creates a single volume, but splits up your data and stripes it across multiple drives. Your computer will read data from all drives simultaneously, so you can read data twice or four times as fast as you can from a single drive (depending on how many drives you have). The same is true for writing data. Most devices use 7,200rpm SATA drives, which read and write data faster than USB 2.0, FireWire or FireWire 800 – so you’ll see little benefit from RAID 0 using these connections. However, a RAID 0 set-up using eSATA is essential for video editors and VFX pros working with HD or uncompressed video.
The downside to RAID 0 is that if any drive in the array fails, you lose all your data. If ensuring your data is safe is most important to you, RAID 1 is your best option. Here, data from one drive is mirrored exactly onto another – so if one fails, the other is intact. Its flaw is that you lose a drive’s worth of capacity.
Four-drive storage systems offer more flexibility, so you could create two sets of RAID 1 mirrored drives, and then stripe them into a RAID 0 array (called RAID 1+0). This gives you fast performance and data security. You also have the option of RAID 5, which uses complex data arrangement to give you total data security, a capacity that’s equal to three of the drives, and faster performance than JBOD – but nowhere near as fast as RAID 0.
The only four-drive system we’ve looked at here is the Drobo, which uses its own proprietary RAID system that allows you to mix and match drive sizes (most RAID systems require equal-sized drives), and automates the process of replacing a failed drive.
The Drobo can also be coupled with the DroboShare device to create a NAS, and run small applications called DroboApps that add extra features. Many of the devices we’ve looked at here include unique functionality – ranging from the Buffalo DriveStation 2Share’s ability to work as a NAS to the Sonnet Fusion F2’s dual-eSATA interface and FireWire powering.
The choice of software is also important if you intend to use your drive for backup. All of the drives we’ve looked at here include some form of backup software – at least for Windows. Many don’t include Mac software, which is a shame as Apple’s own Time Machine backup system has limited flexibility – you can’t just back up set folders for example. Also, be wary of cut-down versions of enterprise-level back-up software, which uses a workflow and terminology that’s alien to non-techies (we’re looking at you here, Retrospect).