When we looked at the first iteration of the Drobo FW800, in April 2008, we had two main criticisms. It was sluggish and expensive.

It's still as expensive – in fact at the time of writing, the cheapest online price from a reputable dealer is £57 more than the first generation – but at least there's the promise of speed, thanks to a meatier processor and the inclusion of FireWire 800 rather than just USB 2.0.

But we're getting ahead of ourselves. What actually is it? Basically, it's a big box with space for up to four 3.5-inch SATA hard disks. Put at least two drives into it – yes, that price is just for the enclosure without any actual storage – and it does something quite clever. Your data is managed internally so that even if one drive fails, you don't lose anything. 'That's just RAID,' you might think, but it actually doesn't use any of the RAID standards.

And that means that it's much smarter than a dual, triple or however-many disk RAID system. Rather than simply filling up, you can slot in more drives at any time, and the Drobo will remap the data on the existing disks to give you more capacity and keep the same redundancy.

Different drive capacities

The real beauty of the system is you don't have to use identical drives. The Drobo makes as much space as possible available from the disks you add, and when all the bays and disks are full, you can – while it's still on and being accessed – pop out the lowest capacity disk and slot in a larger one.

It's designed as a drive that mounts as a single volume on your Desktop, but you can make it network-sharable by adding the £200 DroboShare or plugging it into an AirPort Extreme or Time Capsule. A community of developers is creating apps to run directly on the Drobo too, so you can turn it into, say, an iTunes server or a BitTorrent client.

All this, however, is also true of the first generation Drobo, but this one should be faster, thanks to better firmware, the addition of FireWire 800 and, most importantly, that faster, smarter processor. The good news: it feels much nippier, and is potentially quick enough to be used as primary storage for less demanding users working with SD video. The bad? It's still not fast enough!

It doesn't match the responsiveness of a single low spec drive, and still falls way short of the speed of a true hardware RAID system. For our money, though, the ability to grow the storage pool organically and relatively cheaply – while guarding against hard disk failure – makes the sacrifice in responsiveness worthwhile.