It has been the core technology behind the storage industry since day one, but the sun is setting on traditional RAID technology. After two decades of refinement and fragmentation, we are abandoning the core concepts of disk-centric data protection as storage and servers go virtual. Next-generation storage products will feature refined and integrated capabilities based on pools of storage rather than combinations of disk drives, and we will all benefit from improved reliability and performance.
RAID Classic
Early storage systems were revolutionary, in physically removing storage from the CPU, in enabling sharing of storage between multiple CPUs, and especially in virtualizing disk drives using RAID. When Patterson, Gibson, and Katz proposed the creation of a redundant array of inexpensive disks (RAID) in 1987, they specified five numbered “levels”. Each level had its own features and benefits, but all centered on the idea that a static set of disk drives would be grouped together and presented to higher-level systems as a single drive. Storage devices, as a rule, mapped host data back to these integral disk sets, sometimes sharing a single RAID group among multiple “LUNs”, but never spreading data more broadly. Storage has remained stuck with small sets of drives ever since.
The core insight of the 1980s remains true: More spindles means better performance. Although additional overhead dulls the impact somewhat, the benefit of spreading data across multiple drives can be tremendous. A typical RAID set offers much better performance than the drives alone, and can handle a mechanical failure as a bonus.
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