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Cross-Partition Protocols in a Distributed File Service
Zhang, Zheng; Karamanolis, Christos; Mahalingam, Mallik; Muntz, Daniel
Keyword(s): distributed file system; distributed namespace; fault tolerance; Storage Area Network (SAN)
Abstract: A number of ongoing research projects follow a partition-based approach in order to achieve high scalability for access to the distributed storage service. These systems maintain a namespace that references objects distributed across multiple locations in the system. Typically, atomic commitment protocols (e.g., 2-phase commit) are used for updating the namespace, in order to guarantee its consistency even in the presence of failures. Atomic commitment protocols are known to impose a high overhead to failure-free execution. In addition, they use conservative recovery processes and may considerably restrict the concurrency of overlapping operations in the system. This report proposes a set of new protocols for the implementation of the fundamental operations in a distributed namespace. The protocols use intention logs to impose a minimal overhead to failure-free execution. They are robust against both communication and host failures, and they use aggressive recovery procedures to re-execute incomplete operations. The proposed protocols are compared with their 2-phase commit counterparts and are shown to be strictly better in all critical performance factors: communication round-trips, synchronous I/O, operation concurrency.
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