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Improving Storage System Availability with D-GRAID

Muthian Sivathanu, Vijayan Prabhakaran, Andrea C. Arpaci-Dusseau, and Remzi H. Arpaci-Dusseau


We present the design, implementation, and evaluation of D-GRAID, a gracefully-degrading and quickly-recovering RAID storage array. D-GRAID ensures that most files within the file system remain available even when an unexpectedly high number of faults occur. D-GRAID achieves high availability through aggressive replication of semantically critical data, and fault-isolated placement of logically related data. D-GRAID also recovers from failures quickly, restoring only live file system data to a hot spare. Both graceful degradation and fault-isolated placement are implemented in a prototype SCSI-based storage system underneath unmodified file systems, demonstrating that powerful “file-system like” functionality can be implemented within a “semantically-smart” disk system behind a narrow block-based interface.


Publication typeArticle
Published inACM Transactions on Storage (TOS)
PublisherAssociation for Computing Machinery, Inc.
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