AbstractÐThis paper presents a new distributed disk-array architecture for achieving high I/O performance in scalable cluster computing. In a serverless cluster of computers, all distributed local disks can be integrated as a distributed-software redundant array of independent disks (ds-RAID) with a single I/O space. We report the new RAID-x design and its benchmark performance results. The advantage of RAID-x comes mainly from its orthogonal striping and mirroring (OSM) architecture. The bandwidth is enhanced with distributed striping across local and remote disks, while the reliability comes from orthogonal mirroring on local disks at the background. Our RAID-x design is experimentally compared with the RAID-5, RAID-10, and chained-declustering RAID through benchmarking on a research Linux cluster at USC. Andrew and Bonnie benchmark results are reported on all four disk-array architectures. Cooperative disk drivers and Linux extensions are developed to enable not only the single I/O space, but also the shared virtual memory and global file hierarchy. We reveal the effects of traffic rate and stripe unit size on I/O performance. Through scalability and overhead analysis, we find the strength of RAID-x in three areas: 1) improved aggregate I/O bandwidth especially for parallel writes, 2) orthogonal mirroring with low software overhead, and 3) enhanced scalability in cluster I/O processing. Architectural strengths and weakness of all four ds-RAID architectures are evaluated comparatively. The optimal choice among them depends on parallel read/write performance desired, the level of fault tolerance required, and the cost-effectiveness in specific I/O processing applications.

We propose a lightweight process migration mechanism and an adaptive memory prefetching scheme called AM-

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Support of Single System Image (SSI) services is the main approach that enables better utilization of PC/workstation clusters. Some SSI services can be easily built with the support of other low-level, elementary, SSI services. In this paper, we describe a Single I/O Space architecture for achieving a SSI at the I/O subsystem level. Furthermore, we demonstrate how the Single I/O Space can facilitate the development of other key SSI services. Typical SSI services which can benefit from the Single I/O Space include single file hierarchy, single memory space, checkpointing systems and single process space with process migration facilities. Benchmark performance results show that our design achieves both performance and storage size scalabilities that are essential to building I/O-intensive clusters.

In a serverless cluster of PCs or workstations, the cluster must allow remote file accesses or parallel I/O directly performed over disks distributed to all client nodes. We introduce a new distributed disk array, called the RAID-x, for use in serverless clusters. The RAID-x architecture is based on an orthogonal striping and mirroring (OSM) scheme, which exploits full-bandwidth and protects the system from all single disk failures.The performance of the RAID-x is experimentally proven superior to RAID-1 and NFS in the Linux cluster environment. We propose a new striped checkpointing scheme, leveraging on striped parallelism and pipelined writing of successive disk stripes. This RAID-x architecture greatly enhances the throughput, reliability, and availability of scalable clusters. It appeals especially to I/O-centric cluster applications.