RAID versus JBOD in storage-intensive SANS
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JBOD (Just a Bunch of Disks) is often promoted as a cheaper alternative to a RAID array for applications such as SANs that use a lot of storage. Unlike RAID, which is organized in various manners, many of which offer redundancy and error recovery, JBOD is simply treated as one or more large disk drives. Like RAID, data may be striped across the physical disks in a JBOD for better performance.
While JBOD is definitely cheaper, Piyush Patel, director of multimedia and digital communications at Northern Oklahoma College (Tonkawa, OK) (www.mmdclab.com) has definite opinions based on his experience with the schools 23-seat SAN-connected digital video creation and editing lab. The application is storage intensive because of the number of large files the students generate and share.
"Go with RAID," he says. "We didn't because of the cost. Yes [RAID] costs more, but is it worth losing data to save money?" Northern Oklahoma College went with JBOD for its multi-media lab because of the cost and Patel says that was a mistake. The college's 23-seat multi-media lab puts intensive demands on its storage as students work at least eight hours a day, six days a week learning to produce digital video and do character animation. "We've got 48 drives and if one of them goes down, we're in trouble," says Patel.
The school backs up to tape using an Exabyte Mammoth library that connects via Fibre Channel to the lab's SAN, but even so, losing a drive would be a major disruption in the school's intensive instructional schedule. "In three years we have had one drive go dead and it's just a matter of time before another one goes dead too," Patel says.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.
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The Raidbook : A Handbook of Storage Systems Technology
Author : Paul Massiglia
Publisher : Prentice Hall
The RAIDbook, put out by the RAID advisory board, is the definitive technical handbook on Redundant Arrays of Independent Disks (RAID) and other modern data storage technologies. This is a must-have book for system managers, engineers, and programmers who need to understand high-end hard disk systems.