Aug 14 2007

Ruggedized and Removable

Can removable disk storage break the tape?

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Pity the poor soul who manages backup and archiving in an organization. It is a life full of many forms of frustration: multiple devices to manage, stacks and stacks of odd media formats — DDS, DDS-3, LTO-2, DLT — and media write errors.

In the last few years, fixed disk capacities, average file sizes and data retention policies have combined to greatly expand the scope of what needs to be preserved and for how long. The result is that tape technologies are stretched to the limit. With single-server drives of 300 gigabytes not uncommon, even the most advanced tape technologies are hard pressed to keep up.

The increasing costs and longer backup times of high-capacity tape have prompted many organizations to begin using cheap external hard drives as an alternative. But portable USB or FireWire-based external disks present problems of their own. They can be difficult to manage with major backup software, and the devices themselves are not even as rugged as the run-of-the-mill tape cartridge.

Enter removable disk storage technology. Ruggedized RDX removable cartridges hold 2.5-inch disk drives that work with the RDX drive dock, which comes in USB 2.0 and SATA varieties. The promise is a perfect marriage between disk-to-disk transfer speeds and the portability and storability of tape-based cartridges.

ProStor released RDX to the market in late 2006, first licensing the technology to Tandberg Data. By April 2007, removable storage heavyweight Imation also released RDX drives and docks.

End-User Advantages

RDX drive cartridges come in 40-, 80-, 120- and 160-gigabyte sizes. Each dock is compatible with all available sizes of drive cartridges, and ProStor’s specification calls for all future docks to be backward compatible with older drive cartridges, even as the cartridge capacities increase. Furthermore, each cartridge is ruggedized to survive a 1-meter drop onto concrete, according to ProStor. 

As for performance, I achieved reliable backup speeds of between 700 megabytes per minute and 1 gigabyte per minute in a production environment using the Tandberg USB 2.0 RDX device on a Windows 2003 R2 server with a SATA RAID 1 array running Symantec Backup Exec 11d. Restore speeds are in excess of 1GB per minute in this environment.

For the technician who has to deal with daily backups, RDX might deliver a significant improvement in quality of life with familiar media form factors and rotation methods plus the advantage of disk-to-disk transfer speeds.

Why It Works for IT

A familiar package and methodology combined with a form factor that will grow at the same rate as conventional hard drives makes RDX compelling for the IT manager.

Disk capabilities are expanding faster than tape, and disk is becoming more cost effective. The 160GB Imation Internal SATA RDX drive retails for $483, an attractive price for small businesses. The Tandberg Data LTO-4 SAS Internal drive costs $4,040 for a high-capacity backup system. While 160GB RDX media are more than twice as expensive as Ultrium LTO-4 tape media — $299 versus $134 — the big difference in capital expenditure for LTO over RDX mitigates the increased cost for the drive.


RDX shares the disadvantage of all new technologies: It is unproven. Sure, the promise is there, but who wants to be the first one to find out about potential manufacturing defects? Other questions hang in the air: Will the cartridges hold up to repeated use? RDX does use off-the-shelf hard drives, albeit only those that meet certain specs. And the only mean-time-to-failure information we have on the 2.5-inch drive so far comes from the manufacturer.

Another concern is whether current backup software will support RDX. ProStor announced in April that RDX had been certified compatible with backup and recovery software products CA ARCserve Backup, EMC Retrospect, Symantec Backup Exec and Yosemite Backup. I can’t vouch for all of them, but I found Symantec Backup Exec 11d recognized the Tandberg RDX drive as removable “tape” storage with a minimum of hassle.

CDW Price: $483

Connor W. Anderson is a senior director of IT services at Effective Networking in Clinton, Iowa.