As storage systems evolve, the block-based design of today's disks is becoming inadequate. As an alternative, objectbased storage devices (OSDs) offer a view where the disk manages data layout and keeps track of various attributes about data objects. By moving functionality that is traditionally the responsibility of the host OS to the disk, it is possible to improve overall performance and simplify management of a storage system. The capabilities of OSDs will also permit performance improvements in parallel file systems, such as further decoupling metadata operations and thus reducing metadata server bottlenecks.In this work we present an implementation of the Parallel Virtual File System (PVFS) integrated with a software emulator of an OSD and describe an infrastructure for client access. Even with the overhead of emulation, performance is comparable to a traditional server-fronted implementation, demonstrating that serverless parallel file systems using OSDs are an achievable goal.
Managing concurrency is a fundamental requirement for any multi-threaded system, frequently implemented by serializing critical code regions or using object locks on shared resources. Storage systems are one case of this, where multiple clients may wish to access or modify on-disk objects concurrently yet safely. Data consistency may be provided by an inter-client protocol, or it can be implemented in the file system server or storage device.In this work we demonstrate ways of enabling atomic operations on object based storage devices (OSDs), in particular, the compare-and-swap and fetch-and-add atomic primitives. With examples from basic disk resident data structures to higher level applications like file systems, we show how atomics-capable storage devices can be used to solve consistency requirements of distributed algorithms. Offloading consistency management to storage devices obviates the need for dedicated lock manager servers.
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