Toshiba is working towards doubling the storage capacity of its 0.85-inch hard-disk drive.

The drive is physically the smallest available from any disk drive maker. It went into mass production earlier this year and can store up to 2GB of data in its first-generation form. Toshiba is currently working on a new version that will include two disk platters, allowing it to store up to 4GB of data, said Midori Suzuki, a spokeswoman for Toshiba.

Mass production of the 4GB drive is planned for mid-2005. The company said it has customers for the drive, but wouldn't say who.

Toshiba's drive offers a size and weight advantage over competing drives but falls short in one important area: storage capacity. The root of the drive's strength and weakness can be found in the disk platter, which is 0.85-inches (21.6 millimetres) in diameter while those in competing drives are 1-inch in diameter. The smaller platter allows for a physically smaller drive but also offer less space on which to store data.

Adding an extra platter to the drive will make it slightly thicker. The current model is 3.3 mm thick while the new drive will be 5 mm thick. This is the same thickness as Hitachi Global Storage Technologies Inc.'s 6GB Microdrive but the Toshiba model is still smaller, at 24 mm by 32 mm, compared with the Microdrive at 36 mm by 43 mm. Both drives offer roughly equivalent performance.

Greater capacity will be important if Toshiba wants to keep pace with its competitors. Hitachi is planning a new Microdrive of between 8-10GB capacity before the end of this year, and is looking to employ advanced perpendicular recording technology in future drives to achieve a capacity of around 20GB in 2007.