RAID Organizations for Improved Reliability and Performance: A Not Entirely Unbiased Tutorial (1st revision)

RAID proposal advocated replacing large disks with arrays of PC disks, but as the capacity of small disks increased 100-fold in 1990s the production of large disks was discontinued. Storage dependability is increased via replication or erasure coding. Cloud storage providers store multiple copies of data obviating for need for further redundancy. Varitaions of RAID based on local recovery codes, partial MDS reduce recovery cost. NAND flash Solid State Disks - SSDs have low latency and high bandwidth, are more reliable, consume less power and have a lower TCO than Hard Disk Drives, which are more viable for hyperscalers.Comment: Submitted to ACM Computing Surveys. arXiv admin note: substantial text overlap with arXiv:2306.0876

Almost complete address translation (ACATS) disk array declustering

We present a novel declustering scheme (ACATS) for reliability stripes in an orthogonal disk array. Our scheme is deterministic, run-time efficient, and provides frequently the best possible and always an almost best possible distribution of failure-induced incremental rebuild workloads. Our scheme provides protection against single disk as well as single string failures within the disk array. Our approach presents a framework in which the Level 5 RAID organization logically appears as a Level 4 RAID; it facilitates the provision of distributed sparing in exactly the same manner. ACATS does not require the existence of a suitably configured block design or of a run-time efficient pseudo-random number generator; it is applicable to arbitrarily configured orthogonal disk arrays. Our scheme is faster than declustering schemes that use pseudo-random permutations and achieves better uniformity of disk loads during a disk rebuild; it is simpler than schemes based on block designs. ACATS provides a rich spectrum of declustering schemes. 1