Minuet: Rethinking Concurrency Control in Storage Area Networks.
ABSTRACT Clustered applications in storage area networks (SANs), widely adopted in enterprise datacenters, have tradition- ally relied on distributed locking protocols to coordi- nate concurrent access to shared storage devices. We examine the semantics of traditional lock services for SAN environments and ask whether they are sufficient to guarantee data safety at the application level. We ar- gue that a traditional lock service design that enforces strict mutual exclusion via a globally-consistent view of locking state is neither sufficient nor strictly necessary to ensure application-level correctness in the presence of asynchrony and failures. We also argue that in many cases, strongly-consistent locking imposes an additional and unnecessary constraint on application availability. Armed with these observations, we develop a set of novel concurrency control and recovery protocols for clustered SAN applications that achieve safety and liveness in the face of arbitrary asynchrony, crash failures, and network partitions. Finally, we present and evaluate Minuet- a new synchronization primitive based on these protocols that can serve as a foundational building block for safe and highly-available SAN applications.
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Conference Paper: Interfaces for coordinated access in the file system[Show abstract] [Hide abstract]
ABSTRACT: Distributed applications routinely use the file system for coordination of access and often rely on POSIX consistency semantics or file system lock support for coordination. In this paper we discuss the types of coordination many distributed applications perform and the coordination model they are restricted to using with locks. We introduce an alternative coordination model in the file system that uses extended attribute support in the file system to provide atomic operations on serialization variables. We demonstrate the usefulness of this approach for a number of coordination patterns common to distributed applications.Cluster Computing and Workshops, 2009. CLUSTER '09. IEEE International Conference on; 10/2009