The future of enterprise storage may belong to the solid-state drive, but small-form magnetic disks seem to be doing OK in the present.

New lines of 2.5-inch drives, ostensibly targeted at the laptop market but finding homes in desktops, servers and RAID arrays as well, are pushing both speed and storage capacity well into enterprise levels.

Western Digital recently took the wraps, literally, off the 10,000 rpm VelociRaptor SATA II drive. The 2.5-inch drive offers a respectable 300 GB capacity and a 3 Gbps SATA II interface, but was couched in a 3.5-inch form factor to accommodate a built-in heat sink. A new, lower-power design turned the device into a true 2.5-inch drive, suitable for 1 and 2 RU blade server rack trays.

Toshiba has increased the capacity of its 2.5-inch models to 400 GB, which is still shy of some rival systems, although the company is able to hit that mark with just two spinning platters rather than three. Toshiba has figured out a way to up the density per plate to 200 GB, which was a milestone reached by 3.5-inch technology only last year. It probably won't be long before we see a 600 GB drive.

LaCie, meanwhile, is looking to pair up 2.5-inch drives into mini, mobile RAID arrays that let you take up to 1 TB on the road. The company's Little Big Disk Quadra features a pair of drives in a RAID 0 array that can deliver a burst transfer rate of 110 MBps with eSATA or 80 MBps with FireWire 800. The device weighs less than two pounds and is fully compatible with Leopard and Vista. It also features EMC backup technology and can be linked to additional hard disks or DVD drives.

And while Seagate drew headlines earlier this month with the 1.5 TB Barracuda drive, the new 2.5-inch Momentus drives, the 5400.6 and the 7200.4, are no slouches either. They both come with 3 Gbps SATA interfaces and offer up to 500 GB capacity. The 5400 holds an 8 MB cache, while the 7200 has 16 MB.

Larger disk drives will always hold more data, but they also consume more power. So for the time being, data centers will have to weigh their storage needs carefully against their energy budgets. Ultimately, though, many experts predict the smaller devices will supplant the larger ones; that is, until the price of flash storage comes down to the point where it provides a more universal solution.