Exclusive Review When is a mobile hard drive not a mobile hard drive? When it's LaCie's Little Big Disk, it seems. While the product is certainly portable and - crucially for a mobile unit - doesn't need a separate mains power supply, anyone who's used one of LaCie's compact Pocket Drives will surely look at the chunky, metal-cased LBD and wonder if the company isn't a few platters short of a drive...

But there's method to this apparent madness, and the LBD is aptly named. Stand it on the bundled base plate and it's barely taller and longer than the Pocket Drives of old. It's more than twice as thick, however, and there's a good reason for the extra width: the LBD contains not one but two 2.5in, 7,200rpm hard disks to provide its 200GB storage capacity.

Connect the unit to a Mac or PC - there are a pair of Firewire 800 ports, one Firewire 400 connector and a singe USB 2.0 port for the purpose - and the LBD appears as a single unit. But the drive's circuitry "stripes" whatever you save on the LBD across both disks. It's an approach called RAID 0, and it's done for speed. Alas, there's no way to access both disks separately, so you can't set it up so that, say, one disk mirrors the other in case either fails. No, this is simply about increasing the capacity of mobile drives and making them fast.

LaCie is pitching the LBD's speed more than its portability. The designer aluminium case, which looks not unlike a heatsink, may look cool alongside a PowerBook G4, MacBook Pro or Power Mac G5, but it weighs no less than 650g. Having two drives to power means that only Firewire connections can provide enough juice to run the unit off the bus - so folk relying on its USB 2.0 connectivity, or who have a four-pin Firewire port spare, will still need to connect up the bundled mains adaptor.

Credit to LaCie, it has made the AC power block as small as possible - it's little bigger than a phone charger. It has also bundled a full set of Firewire 800, Firewire 400 and USB 2.0 cables.

The metal case, with its ribbed sides and a flat front broken only by a large, eye-like blue activity light, isn't unattractive in an industrial kind of way. And it looks much better than any number of portable drives that have been decked out in metallic grey plastic. I mentioned the LBD's particular co-ordination with pro-oriented Macs, and this is no co-incidence. The LBD will connect to a PC, but professional Mac users are LaCie's target audience.

Quite apart from the looks, the drive ships already formatted in Apple's HFS+. Windows users will need to reformat the drive - easy enough to do, and you'll recover a little more usable storage capacity - or use the bundled 30-day demo of MacDrive, a Windows-based tool for reading Mac disks.

LaCie also includes a free back-up app with the drive, 1-Click Backup, in both Windows and Mac OS X forms. It simply copies your home folder - or a custom collection of folders - across to the drive, date stamping the target folder accordingly. It doesn't do a sequential back-up - in other words, copying only those files that have changed since you last ran the software - so you'll need to delete back-up folders manually as time passes. 1-Click Backup is fine for individuals, though there's no in-built automation to ensure your data's copied even if you forget to press the button. With the ability to choose which folders are archived, it's much easier to do back-up with 1-Click than it is to drag and drop all of them manually.

I first tried the LBD out on an 867MHz PowerBook G4 with 640MB of RAM and a Firewire 400 port. Copying over a 1.2GB folder full of JPEG images yielded a mean data transfer speed of 12.73MBps - 33 per cent faster than an old 20GB Pocket Drive could manage. Duplicating the data on the disk was faster still, with the LBD delivering a transfer rate of 15.78MBps to the Pocket Drive's 6.52MBps.

To try out the Firewire 800 connectivity, I used a dual-2.3GHz Power Mac G5 with 512MB of 333MHz DDR 2 memory. The machine was very kindly provided for the purpose by computer reseller and Mac specialist Micro Anvika, which let me pop into its busy Chenies Street, London branch to conduct the testing.

Connected to one of G5's two Firewire 800 ports, the LBD copied over the data at a rate of 28.52MBps - 124 per cent faster than I got off the Firewire 400 bus on the G4. I also ran Xbench 1.2, and while the Firewire 800 configuration led by only single-digit percentages in the random read and write tests, on the sequential reads and writes, it yielded improvements of between 31.77 per cent (read, 4KB blocks) and 100.85 per cent (read, 256KB blocks). On the sequential write tests, using 4KB and 256KB blocks, respectively, the gains were 87.76 per cent and 50.28 per cent, respectively.

I also ran the test on the G5's own 3.5in, 250GB, 7,200rpm Serial ATA HDD for a rough comparison. The LDB was half the speed in random 256KB-block reads - Serial ATA is much faster than Firewire 800 - but was 17.24 per cent faster on sequential reads, suggesting the RAID 0 striping delivered a real speed benefit during the test.

All this comes at a price, mind. LaCie will want £509 (including VAT) for the 200GB LBD when it ships in the UK next month. It's also going to offer 160GB, 240GB and 320GB versions, priced at £289, £509 and £579, but these will contain 5,400rpm drives with a combined 8MB of cache - the 200GB model has a 16MB cache - so they're going to be slower.

For £289 you could also buy LaCie's own 500GB Big Disk Extreme, which also supports Firewire 800 and 400, and USB 2.0. If it's portability you want, the best-value LaCie mobile drive is its 100GB Porsche-designed Mobile Hard Drive, for which it wants £179, though you don't get Firewire 800.

But, again, it will be slower, a factor that may not matter so much to most buyers in the market for a mobile hard drive, but will be a cause for concern to users for whom high speed drives are essential, such as video professionals. For them, the LBD's mix of portability and performance will make it worthy of consideration.

Verdict

With a high storage capacity for a portable drive and integrated RAID 0 to boost Firewire 800 performance, but with a steep asking price and a chunky, weighty metal carapace, LaCie's Little Big Disk is aptly named. For consumers and notebook users in business, it may prove insufficiently little in size and priced too big. But for performance-hungry professionals, it has plenty to offer in its compact, industrial-looking casing. ®