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Howard Marks
Howard Marks
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What Comes After RAID? Erasure Codes

As I mentioned a few blog entries ago, the basic math behind parity based RAID (Redundant Array of Inexpensive Drives) solutions is starting to break down. While I think it's important for those of us that spend our days thinking about these things to raise the alarm, it's more important to think and write about the technologies that can take us past parity RAID. One major contender is Reed-Solomon erasure codes, which vendors are starting to use as an efficient alternative to parity or mirrorin

Cleversafe  also points out that dispersal codes don't, like common RAID, store data in some blocks and ECC information in others, but instead transforms all the data so each block contains encoded data and forward error correction information. It therefore requires a minimum set of blocks to be able to recover any data. Disk drives holding less than the minimum number of blocks are effectively encrypted and a "Black hat" couldn't scan the disk for social security numbers or other small but sensitive data items that could be on an orphaned drive from a RAID set.

Now, both NEC and Cleversafe are targeting their solutions at secondary storage applications where latency isn't a major concern.  I wonder how erasure codes will work their way into more mainstream applications.

Howard Marks is founder and chief scientist at Deepstorage LLC, a storage consultancy and independent test lab based in Santa Fe, N.M. and concentrating on storage and data center networking. In more than 25 years of consulting, Marks has designed and implemented storage ... View Full Bio
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