@Article{holland:on-line,
  author = {Mark Holland and Garth A. Gibson and Daniel P. Siewiorek},
  title = {Architectures and Algorithms for On-Line Failure Recovery in
  Redundant Disk Arrays},
  journal = {Journal of Distributed and Parallel Databases},
  year = {1994},
  month = {July},
  volume = {2},
  number = {3},
  pages = {295--335},
  URL =
  {http://www.cs.cmu.edu/afs/cs.cmu.edu/project/pdl/ftp/Declustering/DAPD.ps},
  keywords = {parallel I/O, disk array, RAID, redundancy, reliability,
  pario-bib},
  abstract = {The performance of traditional RAID Level 5 arrays is, for many
  applications, unacceptably poor while one of its constituent disks is
  non-functional. This paper describes and evaluates mechanisms by which this
  disk array failure-recovery performance can be improved. The two key issues
  addressed are the data layout, the mapping by which data and parity blocks
  are assigned to physical disk blocks in an array, and the reconstruction
  algorithm, which is the technique used to recover data that is lost when a
  component disk fails. \par The data layout techniques this paper investigates
  are instantiations of the declustered parity organization, a derivative of
  RAID Level 5 that allows a system to trade some of its data capacity for
  improved failure-recovery performance. We show that our instantiations of
  parity declustering improve the failure-mode performance of an array
  significantly, and that a parity-declustered architecture is preferable to an
  equivalent-size multiple-group RAID Level 5 organization in environments
  where failure-recovery performance is important. The presented analyses also
  include comparisons to a RAID Level 1 (mirrored disks) approach. \par With
  respect to reconstruction algorithms, this paper describes and briefly
  evaluates two alternatives stripe-oriented reconstruction and disk-oriented
  reconstruction, and establishes that the latter is preferable as it provides
  faster reconstruction. The paper then revisits a set of previously-proposed
  reconstruction optimizations, evaluating their efficacy when used in
  conjunction with the disk-oriented algorithm. The paper concludes with a
  section on the reliability versus capacity trade-off that must be addressed
  when designing large arrays.}
}