Imation, the world's biggest tape media manufacturer, has entered the removable hard drive market, announcing its own Odyssey removable drives even as it continues making cartridges for the competing ProStor RDX format.

Unlike tape cartridges, disk cartridges include the drive motor and electronics as well as the read/write head. These delicate mechanisms have to be ruggedised to withstand the handling involved in drive insertion and ejection and storing on shelves.

Odyssey cartridges use 2.5-inch serial ATA (SATA) drives with 40, 80 or 120GB capacities. The cartridges claim to withstand a 900G shock, equivalent to a 1 metre drop onto a concrete floor, and have a safety mechanism to avoid static electricity build-up. They fit into an external USB-connected docking station which can transfer data at 25MB/s. An internal docking unit will become available at a future date.

The products comes with EMC Retrospect backup software, which includes an encryption facility.

Imation is also making RDX drive cartridges under license from ProStor. These can be used in Tandberg's RDX QuikStor or Dell PowerVault RD1000 docking stations. These can be either SATA-connected internal units or USB-connected external ones. The SATA transfer rate is 45MB/sec.

The 2.5-inch SATA RDX drives have capacities of 40, 80, 120 or 160GB, and are embedded in ruggedised cartridges with internal shock absorbers. They can also withstand a 1 metre drop. The RDX cartridge has a mean time between failures (MTBF) of 500,000 hours and load/unload cycle of 5,000 insertions. (Quantum's GoVault cartridge is also good for 5,000 insertions but its MTBF is 375,000 hours.)

For comparison a Seagate Savvio 2.5-inch drive has a 1.6 million hour MTBF. Removability drastically shortens the MTBF figure.

Pricing information and comparisons

The price for a 40GB Imation Odyssey cartridge and docking station is $249, with $349 buying a docking station and 120GB cartridge. These prices are lower than those from Dell, Quantum and Tandberg for eqivalent products.

On announcement a Dell RD1000 40GB cartridge and internal SATA docking unit cost $300 with $500 getting you a 120GB cartridge and external USB docking station.

A Tandberg RDX QuikStor comes with Symantec Backup Exec QS and costs £162 ($299) for an internal docking unit and 40GB cartridge. A 40GB cartridge costs £65 ($120), an 80GB one £121. An external docking unit is £222 with a 40GB cartridge.

Quantum's competing GoVault removable drive format comes with 40, 80 or 120GB drive capacities. A 40GB GoVault cartridge costs $149. It's internal docking unit uses SATA connectivity, transfers data at around 20MB/sec, and, with a 120GB cartridge, costs about $420