Enterprises are keeping more data online for longer periods of time, much of it ending up on high-capacity SATA disk drives requiring lengthy rebuild times when a drive failure occurs. But self-healing storage systems, an emerging class of storage products, pick up where today's RAID configurations leave off, using heuristics, journaling, read parity correction and distributed data resiliency in conjunction with RAID 6 for higher levels of performance and data protection.

Arun Taneja, consulting analyst and founder of the Taneja Group, Hopkinton, MA, finds that SATA disk drives are at the core of most data protection strategies. The question companies need to ask themselves, says Taneja, is whether or not RAID alone is an adequate level of data protection when it comes to SATA. "RAID does not do anything to minimize the horrendous rebuild times of a single 1TB drive failure in an array group," he says.

Mark Seager, assistant department head for advanced technology at the Lawrence Livermore National Laboratory (LLNL) in Livermore, CA, says the individual SATA disk drives on his DataDirect Networks S2A storage system occasionally act quirky. "From time to time, individual SATA drives go catatonic from a half a second to a couple of seconds," says Seager.

DataDirect Networks uses heuristics and journaling to address this unresponsive condition on SATA drives. When a drive fails to respond, the S2A storage system marks the drive as failed, but doesn't

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immediately treat the drive as if it's actually failed. It takes the drive offline, journals writes to that drive, and then attempts are made to reset and reinitialize the drive before marking it as failed.

"If the drive has truly failed, this process causes no harm and the S2A storage system starts the rebuild. If the drive still works, the S2A storage system saves the drive and users are spared a lengthy rebuild time," say Josh Goldstein, DataDirect Networks' VP of product marketing.

Unlike enterprise-class SAS and Fibre Channel (FC) drives that include error correction such as parity checks on reads in their firmware, SATA drives have no such feature in their software. Self-healing storage systems address this according to whether their intended purpose is for production or to archive and back up data.

This was first published in September 2007

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