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Alternatives to RAID

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BeyondRAID: Data Robotics Inc.'s BeyondRAID sits on top of RAID and makes it completely transparent to the administrator. It transforms RAID from a deterministic offline process into an online dynamic one. Essentially self-managing, BeyondRAID chooses RAID sets based on the required data protection at any given point in time. But it's how BeyondRAID addresses RAID issues that truly makes it stand out. It protects against one or two HDD failures and has built-in automatic data self-healing (not storage self-healing). Data blocks are spread across all of the drives so data reconstruction is very fast. Because the system is "data aware," it allows for different drive sizes, drive re-ordering and proportional rebuild times. Because it tops out at 8 SATA drives, it's most appealing for small- and medium-sized businesses (SMBs), but it's a true turn it on, hook it up and forget it storage system.

RAID paradigm shift: Erasure codes

Erasure codes are designed to separate data into unrecognizable chunks of information with additional information added to each chunk that allows any complete data set to be resurrected from some subset of the chunks. The chunks can be distributed to different storage locations within a data center, city, region or anywhere in the world.

Erasure codes have built-in data security because each individual chunk doesn't contain enough information to reveal the original data set. A large enough subset of chunks from the

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different storage nodes is needed to fully retrieve the total data set, with the number of required chunks determined by the amount of additional information assigned to each chunk. More additional information means fewer chunks are required to retrieve the whole data set.

Erasure codes are resilient against natural disasters or technological failures because only a subset of the chunks is needed to reconstitute the original data. In actuality, with erasure codes there can be multiple simultaneous failures across a string of hosting devices, servers, storage elements, HDDs or networks, and the data will still be accessible in real time.

Also known as forward error correction (FEC), erasure coding storage is a completely different approach than RAID. Erasure codes eliminate all of the RAID issues described here. It's a new approach and at this time only three vendors have erasure code-based products: Cleversafe Inc.'s dsNet, EMC Corp.'s Atmos and NEC's HYDRAstor.

Erasure codes appear to be better suited for large data sets than smaller ones. It's especially appropriate for cloud or distributed storage because it never has to replicate a data set and can distribute the data over multiple geographic locations.

RAID's evolution

The issues with traditional RAID are well known, and are escalating with higher disk capacities. The RAID alternatives described here address many of those problems, and more new approaches are on the way. Selecting the best fit for a particular environment requires research, testing, pilot programs, patience and a willingness to take a risk with a non-traditional approach.

BIO: Marc Staimer is founder and senior analyst at Dragon Slayer Consulting in Beaverton, Ore., a consulting practice that focuses on strategic planning, product development and market development for technology products. You can contact him at marcstaimer@mac.com.

This was first published in May 2010

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