Happy Birthday to RAID, the Storage Solution that Transformed Computing

venustus

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It’s hard to understate the impact of NAND flash and SSDs. Over the last decade, these storage solutions have transformed the entire market. But long before we had massive solid-state storage, we had a different method of improving system performance and response time: RAID. The venerable storage system turned 30 yesterday and it’s stillwidely used in enterprise and server solutions.

The people who invented RAID, David Patterson, Garth Gibson, and Randy Katz, first defined the concept in 1987, followed by a formal paper in 1988. Specific concepts like mirroring had been defined a decade previously, but RAID didn’t just allow for a mirrored solution. It also provided a blueprint for dramatically accelerating disk performance by striping data across multiple drives at the same time.

Patterson, Gibson, and Katz defined a variety of RAID levels to suit various tasks and strategies. Today, RAID 2 and RAID 3 are rarely used, while motherboards typically offer software RAID support for RAID 0, RAID 1, and RAID 10. Some boards and controllers also support RAID 5. RAID 0 is data-striping only–you get the advantage of writing data to two disks at once (boosting performance), but you increase the chance of catastrophically losing data. If each drive has a 1 percent chance of failure (just as an example), then the chances of losing a drive and all of your data is 4 percent, since any failure will kill the array. RAID 1 is mirroring–all of the data on Drive 0 is simultaneously written to Drive 1. This protects data, but offers no performance improvements. RAID 10 (0+1) combines the two methods, as shown below:



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