The RDX cartridge is based on a 2.5" hard drive specially mounted in a plastic shell, improving its shock/vibration performance. Tandberg claims that the RDX cartridges are capable of withstanding a 1 meter (3.3') drop without incurring any damage. We had to put this to the test, so we "accidentally" dropped it from about 3 feet off the ground; subsequent testing confirmed that the drive continued to operate normally.
Tandberg currently offers cartridges in 40, 80 and 120 GB capacities. Our test sample shipped with a 40 GB cartridge, which contains a Fujitsu 2.5" MHV2040BH drive spinning at 5,400 RPM and containing an 8 MB cache. On the top rear end of the cartridge is a write protection switch, which can be switched to read-only, as an added precaution against accidental data deletion.
Our attempt to benchmark the performance of the single drive failed due to the fact that Windows determines that it is a removable device, disallowing the use of standard HDD benchmarks. We also tried to connect the cartridge directly to the system, bypassing the RDX drive; although the Device Manager showed the drive correctly, the Disk Management applet caused problems and did not work as expected.
The sequential transfer performance with uncompressed data was around 28 MB/s, which in fact is close to this hard drive's technical limit. A Fujitsu MHV2120BH had 30 MB/s average write performance, so we can conclude that our measured value is valid.
The Iomega REV drive is also available in this category. Although both companies target tape backup with removable hard disk based solutions, their implementations differ quite significantly.
The REV media contains the disk platters and motor in the cartridge, with the read/write heads contained in the REV drive. On the other hand, RDX cartridges are based on existing 2.5" hard drives and have the disk platters, motor and read/write heads all in a self-contained package.
Both methods have their advantages and disadvantages. The advantage of having the read/write heads in the drive as opposed to the cartridge is higher shock tolerance and lower media production costs. These benefits come at the price of limited compatibility with future media, and lower performance compared to self-contained solutions. On the other hand, while the latter may offer better performance and compatibility with future cartridges, they are significantly more expensive and somewhat more fragile than the REV cartridges.
At the moment, Iomega offers two models with 35 GB and 70 GB capacities, in both internal and external forms. The 70 GB model is backwards compatible with 35 GB media (at a reduced read/write rate), but 70 GB media will not work on 35 GB REV drives. The 70 GB ATAPI model goes for around $470, and its disks are priced at around $60. The RDX QuikStor will cost about $400, which includes an 80 GB cartridge and backup software.