INTRODUCTION Current disk drives have raw data rates of 5 to 10 million bits per second (Mbps) or more. Such rates suffice for many forms of digital audio and motion video (continuous media, or CM) data: audio data rates are from 8 Kbps to 1.4 Mbps, while compressed video ranges from one to several Mbps. However, when a disk is accessed via a general-purpose file system, the data rates seen by clients are generally lower and may vary unpredictably. We have developed a Continuous Media File System (CMFS) whose clients read and write files in "sessions", each with a guaranteed minimum data rate. Multiple sessions, perhaps with different data rates, can coexist. CMFS can handle non-real-time traffic concurrently with these real-time sessions. #################################### Authors' addresses: D.P. Anderson, 1891 East Francisco Blvd. San Rafael, CA 94901. Y. Osawa, MO Business Development Division, Storage Systems Group, Sony

By providing direct data transfer between storage and client, net-work-attached storage devices have the potential to improve scal-ability for existing distributed file systems (by removing the server as a bottleneck) and bandwidth for new parallel and distributed file systems (through network striping and more efficient data paths). Together, these advantages influence a large enough fraction of the storage market to make commodity network-attached storage fea-sible. Realizing the technology’s full potential requires careful consideration across a wide range of file system, networking and security issues. This paper contrasts two network-attached storage architectures-(l) Networked SCSI disks (NetSCSI) are network-attached storage devices with minimal changes from the familiar SCSI interface, while (2) Network-Attached Secure Disks (NASD) are drives that support independent client access to drive object services. To estimate the potential performance benefits of these architectures, we develop an analytic model and perform trace-driven replay experiments based on AFS and NFS traces. Our results suggest that NetSCSI can reduce tile server load during a burst of NFS or AFS activity by about 30%. With the NASD archi-tecture, server load (during burst activity) can be reduced by a fac-tor of up to five for AFS and up to ten for NFS. 1

This paper describes the architecture of eNVy, a large non-volatile main memory storage system built primarily with Flash memory. eNVy presents its storage space as a linear, memory mapped array rather than as an emulated disk in order to provide an efficient and easy to use software interface. Flash memories...

Transmission Control Protocol (TCP) is used by various applications to achieve reliable data transfer. TCP was originally designed for unreliable networks. With the emergence of high-speed wide area networks various improvements have been applied to TCP to reduce latency and achieve improved bandwidth. The improvement is achieved by having system administrators tune the network and can take a considerable amount of time. This paper introduces PSockets (Parallel Sockets), a library that achieves an equivalent performance without manual tuning. The basic idea behind PSockets is to exploit network striping. By network striping we mean striping partitioned data across several open sockets. We describe experimental studies using PSockets over the Abilene network. We show in particular that network striping using PSockets is effective for high performance data intensive computing applications using geographically distributed data. 1. INTRODUCTION With the rapid advancements in networking t...

Recently we presented several disk array architectures designed to increase the data rate and I/O rate of supercomputing applications, transaction processing, and file systems [Patterson 88]. In this paper we present a hardware performance measurement of two of these architectures, mirroring and rotated parity. We see how throughput for these two architectures is affected by response time requirements, request sizes, and read to write ratios. We find that for applications with large accesses, such as many supercomputing applications, a rotated parity disk array far outperforms traditional mirroring architecture. For applications dominated by small accesses, such as transaction processing, mirroring architectures have higher performance per disk than rotated parity architectures.

. Current I/O benchmarks suffer from several chronic problems: they quickly become obsolete, they do not stress the I/O system, and they do not help in understanding I/O system performance. We propose a new approach to I/O performance analysis. First, we propose a self-scaling benchmark that dynamically adjusts aspects of its workload according to the performance characteristic of the system being measured. By doing so, the benchmark automatically scales across current and future systems. The evaluation aids in understanding system performance by reporting how performance varies according to each of five workload parameters. Second, we propose predicted performance, a technique for using the results from the self-scaling evaluation to quickly estimate the performance for workloads that have not been measured. We show that this technique yields reasonably accurate performance estimates and argue that this method gives a far more accurate comparative performance evaluation than tradition...

Multimedia storage servers provide access to multimedia objects including text, images, audio, and video. The design of such servers fundamentally differs from conventional servers due to: (1) the real-time storage and retrieval, as well as (2) the large storage space and data transfer rate requirements of digital multimedia. In this paper, we present an overview of the architectures and algorithms required for designing digital multimedia storage servers.

File system I/O is increasingly becoming a performance bottleneck in large distributed computer systems. lais is due to the increased file I/O demands of new applications, the inability of any single storage structure to respond to these demands, and the slow decline of disk access times (latency and seek) relative to the rapid increase in CPU speeds, memory size, and network bandwidth.

Parallel database systems have to support the effective parallelization of complex queries in multi-user mode, i.e. in combination with inter-query/inter-transaction parallelism. For this purpose, dynamic scheduling and load balancing strategies are necessary that consider the current system state for determining the degree of intra-query parallelism and for selecting the processors for executing subqueries. We study these issues for parallel hash join processing and show that the two subproblems should be addressed in an integrated way. Even more importantly, however, is the use of a multi-resource load balancing approach that considers all potential bottleneck resources, in particular memory, disk and CPU. We discuss basic performance tradeoffs to consider and evaluate the performance of several load balancing strategies by means of a detailed simulation model. Simulation results will be analyzed for multi-user configurations with both homogeneous and heterogeneous (query/OLTP) workloads.

To meet the bandwidth needs of modern computer systems, parallel storage systems are evolving beyond RAID levels 1 through 5. The Parallel Data Lab at Carnegie Mellon University has constructed three Scotch parallel storage testbeds to explore and evaluate five directions in RAID evolution: first, the development of new RAID architectures to reduce the cost/performance penalty of maintaining redundant data; second, an extensible software framework for rapid prototyping of new architectures; third, mechanisms to reduce the complexity of and automate error-handling in RAID subsystems; fourth, a file system extension that allows serial programs to exploit parallel storage; and lastly, a parallel file system that extends the RAID advantages to distributed, parallel computing environments. This paper describes these five RAID evolutions and the testbeds in which they are being implemented and evaluated.