Data Robotics Drobo

The classic image of a robot as a lurching metallic automaton has been challenged in recent years by products like iRobot's Roomba home-roaming vacuum, which looks more like an oversized dinner plate than C-3PO. Now comes the Drobo, a device that looks like an ordinary external hard drive or network attached storage (NAS) unit but which Data Robotics dubs "the world's first storage robot."
That may sound like marketing puffery, but based on's definition of a robot -- a mechanical device that operates automatically with human-like skill -- it may not be far off the mark. It turns out that the $499 Drobo provides storage that's considerably easier to configure and upgrade than any device we've used before.
Its compact size and rectangular shape make the Drobo look like a toaster. Slices of bread -- in the form of standard 3.5-inch internal Serial ATA I or II hard drives, of any capacity, from any manufacturer -- go into four bays that you access by pulling off the Drobo's magnetically attached front cover. Unlike most storage devices with user-accessible bays, Drobo does not require special mounting trays, connectors, or cables to connect the drives -- you simply slide them into each slot until they click into place. Buying the drives is up to you; Drobo's $499 price includes only the chassis.
A large fan channels hot air from the rear of the Drobo. We wouldn't necessarily call it loud, but the fan noise periodically became noticeable over the din of the nearby PC. You connect the Drobo directly to a PC or Mac (using NTFS or HFS+ formatting respectively) via USB 2.0 only. We'd like the device even more if it let us connect through FireWire, eSATA, or even Ethernet; Data Robotics merely says that models with additional interfaces might appear in the future.
You can network the Drobo by connecting it to a USB storage server or NAS device, but since it doesn't support the FAT32 format, this scenario doesn't support full access in a mixed PC/Mac environment. (A Mac can read but not write NTFS, and Windows doesn't understand Apple's HFS+ formatting at all.)
Just Put That Anywhere
When you think of multiple-hard-drive storage, you think of RAID. But while the Drobo does use RAID-style techniques to organize and protect data, it doesn't do it in the customary way. Most notably, RAID requires drives of identical capacity, but the Drobo has no such limitation. Instead, it uses a storage scheme that aggregates different-sized drives into a single volume.
While standard RAID mirrors one disk on another (RAID 1) or stripes parity data across three or more disks (RAID 5), the method the Drobo uses to safeguard your data depends on how many drives you use, what their capacities are, and how much data is on them. The Drobo protects data files rather than disks, so depending on the aforementioned variables it can either mirror or parity-stripe your data. In many cases, it will do both -- mirroring one set of data and striping across disks.
Drobo's approach to data protection reserves a significant chunk of your overall capacity in order to let the unit reorganize your data as needed. This means that there's always free space where Drobo can relocate data in the event of a drive failure. Another huge upside is that this lets you increase the system's capacity whenever you need to, simply by replacing any drive with a larger one. The Drobo can incorporate the added capacity into its storage scheme without any data disruption requiring you to manually rebuild volumes.
Determining how much capacity is left on a standard RAID device after subtracting space used for data protection is a relatively simple calculation -- you lose half of the total with RAID 1 or 10, or 1/x-- where x is the number of drives -- for RAID 5. Figuring out the usable space on the Drobo isn't quite as straightforward, especially with varying drive capacities. A general rule of thumb is to subtract the capacity of the largest drive used; Data Robotics' Web site offers a graphical "Drobolator" utility that lets you calculate usable capacity more precisely.

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