Company’s Profile: Data Robotics

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Entirely manufactured in China, good-looking Drobo is the only disk array with hot-swappable HDDs and where you can replace them with other ones of any capacity. It means the system can evolve just by changing any HDD by next-generation ones of higher capacity with an automatic rebuilding process. On a standard RAID, you can eventually include rotating devices of different capacities, but the capacity of the lower one will be apply to all others. So, what's the secret behind Drobo technology named BeyondRAID by Data Robotics?

"RAID is dead", declared CEO Geoff Barrall when the first Drobo was launched. But Drobo is RAID, and more than that, it's RAIDs, as it uses different levels of disk array inside the machine. The company never reveals precisely what kind of algorithms was included in the controller. Here is what we got looking at the patents.



Here is just an example with a Drobo containing only three disks to simplify the explanation, but it's the same idea with more of them. Suppose that you have inserted in Drobo the following three hard disk drives: 500GB, 1TB and a 2TB units (see diagram). The data are striped (like for RAID-5) on each first 500GB part of the three disks, thus obtaining 2x500GB of user capacity, the other 500GB being filled for protection. Consequently, the first 500GB is completely full. Remaining are raw capacities of 500GB on the 1TB drive, and 1.5TB on the 2TB unit. This time RAID-1 or mirroring is used for the next 500GB written as only two HDDs can be used for this protection. And finally, on the 2TB device, 1TB remains available but cannot be protected at all. This method explains why you can extract any HDD at any time as all its data are protected on other ones to rebuild it.

But in this configuration containing 3.5TB of total raw capacity, you get at the end (only) 2.5TB of user capacity including 1TB not protected, or 43% of the total capacity without risk, 71% if you are a risky guy. In reality, it's a little less than that (40% and 67%) because Drobo needs some space for its own management.

Our conclusion: Drobo is a nice idea but, at the end, the user capacity is much lower than on conventional disk array in RAID-5. You can get better ratio on Drobo if you integrate only HDDs with the same capacity. For example, with three 1TB HDDs, the ratio is much better: 60% of data entirely protected. But if you want to expand, you need to change all the drives to avoid to lose a higher percentage of capacity. To get the exact figures of what you get, Data Robotics offers an easy-to-use calculator on its web site.

Recently, the company released new Drobos with the following starting prices: 8-bay File Sharing Storage for Business ($2,199 USD, €1,649), 8-bay SAN Storage for Business ($3,499 USD, €3,229) and 12-bay SAN Storage for Business ( €8,219, with redundant  power supply, for the first time as rackmount, available in 2Q11), also adding thin provisioning and tiering.
What's missing? Drobo could evolve. In our opinion, Data Robotics has to:

• build a system not only with 3.5-inch but with 2.5-inch HDDs (not using a special 3.5-inch kit, as of today) to finalize a smaller system
• also offer SSDs (it's in the company's roadmap)
• add compression, de-dupe, redundant controller and replication
• propose a complete solution with a backup software