Technical Factors Differentiating RAID Levels

The reason why there are so many different RAID levels is that there are many different ways to configure a bunch of hard disks, and many different needs of RAID users. Distinguishing between different levels isn't easy at times, because many RAID levels are similar to others in various ways. Worse, sometimes the differences between levels seem subtle, but these small discrepancies can have a huge impact on the characteristics of the array and the applications that make sense for it.

To completely and accurately portray each single and multiple RAID level, I describe each in terms of its most important characteristics, including those related to fault tolerance, capacity, performance, cost and other attributes. To avoid duplication, I have provided this section that describes what each of these technical factors or attributes are about. For each one I explain briefly what the attribute means, how it is defined, and how and why it helps differentiate between various RAID levels. In the last sub-section, I also discuss the reasons why some implementers may wish to consider creating more than one array for a system if the needs of that system can't be met by one array type.

Note that in addition to the descriptions in this section, you may also want to take a look at the more general discussions of performance and reliability issues in the section covering general concepts and issues. Some of the pages that follow in this area will refer back to those or other pages in the site's coverage of RAID.

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