Enhanced Reliability Modeling of RAID Storage Systems

  • Authors:
  • Jon G. Elerath;Michael Pecht

  • Affiliations:
  • Network Appliance, Inc.;University of Maryland, USA

  • Venue:
  • DSN '07 Proceedings of the 37th Annual IEEE/IFIP International Conference on Dependable Systems and Networks
  • Year:
  • 2007

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Abstract

A flexible model for estimating reliability of RAID storage systems is presented. This model corrects errors associated with the common assumption that system times to failure follow a homogeneous Poisson process. Separate generalized failure distributions are used to model catastrophic failures and usage dependent data corruptions for each hard drive. Catastrophic failure restoration is represented by a three-parameter Weibull, so the model can include a minimum time to restore as a function of data transfer rate and hard drive storage capacity. Data can be scrubbed as a background operation to eliminate corrupted data that, in the event of a simultaneous catastrophic failure, results in double disk failures. Field-based times to failure data and mathematic justification for a new model are presented. Model results have been verified and predict between 2 to 1,500 times as many double disk failures as that estimated using the current mean time to data loss method.