The Vesta parallel file system is designed to provide parallel file access to application programs running on multicomputers with parallel I/O subsystems. Vesta uses a new abstraction of files: a file is not a sequence of bytes, but rather it can be partitioned into multiple disjoint sequences that are accessed in parallel. The partitioning-which can also be changed dynamically-reduces the need for synchronization and coordination during the access. Some control over the layout of data is also provided, so the layout can be matched with the anticipated access patterns. The system is fully implemented and forms the basis for the AIX Parallel I/O File System on the IBM SP2. The implementation does not compromise scalability or parallelism. In fact, all data accesses are done directly to the I/O node that contains the requested data, without any indirection or access to shared metadata. Disk mapping and caching functions are confined to each I/O node, so there is no need to keep data coherent across nodes. Performance measurements show good scalability with increased resources. Moreover, different access patterns are shown to achieve similar performance.

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Parallel computer architectures require innovative software solutions to utilize their capabilities. This is true for system software no less than for application programs. File system development for the IBM SP product line started with the Vesta research project, which introduced the ideas of parallel access to partitioned files. This technology was then integrated with a conventional AIX environment to create the IBM AIX Parallel I/O File System product. We describe the design and implementation of Vesta, including user interfaces and enhancements to the control environment needed to run the system. Changes to the basic design that were made as part of the IBM AIX Parallel I/O File System are identified and justified.