For many emerging and existing architectures, NAND flash is the storage media used to fill the cost-performance gap between DRAM and spinning disk. However, while NAND flash is the best of the available options, for many workloads its specific design choices and trade-offs are not wholly suitable. One such workload is long-running scientific applications which use checkpoint-restart for failure recovery. For these workloads, HPC data centers are deploying NAND flash as a storage acceleration tier, commonly called burst buffers, to provide high levels of write bandwidth for checkpoint storage. In this paper, we compare the costs of adding reliability to such a layer versus the benefits of not doing so. We find that, even though NAND flash is non-volatile, HPC burst buffers should not be reliable when the performance overhead of adding reliability is greater than 2%.

This paper presents scheduling and admission control algorithms for access to processor and storage resources of a video file server. The scheduling algorithms support multiple classes of tasks with diverse performance requirements, allow for the co-existence of guaranteed real-time requests with sporadic, and unsolicited requests, and ensure system stability during overloads. Performance guarantees are maintained for real-time streams in the presence of unpredictably varying non real-time traffic. A prototype video file server was implemented on an Intel 486 platform. Performance results show that a large number of streams can be supported, while maintaining efficient utilization of system resources.

Over the last few years, there have been several efforts to use logging to improve performance, reliability, and recovery times of file systems. The two major techniques are metadata logging, where the log records metadata changes and is a supplement to the on-disk file system, and log-structured file systems, whose log is their only on-disk representation. When the file system is mainly or wholly accessed through the Network File System (NFS) protocol, it adds new considerations to the suitability of the logging technique. NFS requires that all operations be updated to stable storage before returning. As a result, file system implementations that were effective for local access may perform poorly on an NFS server. This paper analyzes the issues regarding the use of logging on an NFS server, and describes an implementation of a BSD Fast File System (FFS) with metadata logging that performs effectively for a dedicated NFS server.