Robo-line storage: Low latency, high capacity storage systems over geographically distributed networks

Rapid advances in high performance computing are making possible more complete and accurate computer-based modeling of complex physical phenomena, such as weather front interactions, dynamics of chemical reactions, numerical aerodynamic analysis of airframes, and ocean-land-atmosphere interactions. Many of these 'grand challenge' applications are as demanding of the underlying storage system, in terms of their capacity and bandwidth requirements, as they are on the computational power of the processor. A global view of the Earth's ocean chlorophyll and land vegetation requires over 2 terabytes of raw satellite image data. In this paper, we describe our planned research program in high capacity, high bandwidth storage systems. The project has four overall goals. First, we will examine new methods for high capacity storage systems, made possible by low cost, small form factor magnetic and optical tape systems. Second, access to the storage system will be low latency and high bandwidth. To achieve this, we must interleave data transfer at all levels of the storage system, including devices, controllers, servers, and communications links. Latency will be reduced by extensive caching throughout the storage hierarchy. Third, we will provide effective management of a storage hierarchy, extending the techniques already developed for the Log Structured File System. Finally, we will construct a protototype high capacity file server, suitable for use on the National Research and Education Network (NREN). Such research must be a Cornerstone of any coherent program in high performance computing and communications

Diskless supercomputers: Scalable, reliable I/O for the Tera-Op technology base

Computing is seeing an unprecedented improvement in performance; over the last five years there has been an order-of-magnitude improvement in the speeds of workstation CPU's. At least another order of magnitude seems likely in the next five years, to machines with 500 MIPS or more. The goal of the ARPA Teraop program is to realize even larger, more powerful machines, executing as many as a trillion operations per second. Unfortunately, we have seen no comparable breakthroughs in I/O performance; the speeds of I/O devices and the hardware and software architectures for managing them have not changed substantially in many years. We have completed a program of research to demonstrate hardware and software I/O architectures capable of supporting the kinds of internetworked 'visualization' workstations and supercomputers that will appear in the mid 1990s. The project had three overall goals: high performance, high reliability, and scalable, multipurpose system

Tcl and the Tk Toolkit

This book is about two packages called Tcl and Tk. Together they provide a programming system for developing and using graphical user interface (GUI) applications. Tcl stands for "tool command language" and is pronounced "tickle"; is a simple scripting language for controlling and extending applications. It provides generic programming facilities that are useful for a variety of applications, such as variables and loops and procedures. Fur-thermore, Tcl is embeddable: its interpreter is implemented as a library of C procedures that can easily be incorporated into applications, and each application can extend the core Tcl features with additional commands specific to that application

The Role of Distributed State

Distributed state offers the potential for improving the performance, coherency, and reliability of distributed systems. Unfortunately, distributed state also introduces consistency problems, crash sensitivity, time and space overheads, and complexity; these problems make it difficult to achieve the potential benefits. This paper describes the advantages and disadvantages of distributed state, and presents the NFS and Sprite file systems as examples of different tradeoffs. It does not appear possible to achieve all the advantages of distributed state and also avoid all the problems; rather, system designers must make compromises based on the needs of their individual environments

Scripting: Higher-Level Programming for the 21st Century

Scripting languages such as Perl and Tcl represent a very different style of programming than system programming languages such as C or JavaTM. Scripting languages are designed for "gluing " applications; they use typeless approaches to achieve a higher level of programming and more rapid application development than system programming languages. Increases in computer speed and changes in the application mix are making scripting languages more and more important for applications of the future

An X11 Toolkit Based on the Tcl Language

This paper describes a new toolkit for X11 called Tk. The overall functions provided by Tk are similar to those of the standard toolkit Xt. However, Tk is implemented using Tcl, a lightweight interpretive command language. This means that Tk's functions are available not just from C code compiled into the application but also via Tcl commands issued dynamically while the application runs. Tcl commands are used for binding keystrokes and other events to application-specific actions, for creating and configuring widgets, and for dealing with geometry managers and the selection. The use of an interpretive language means that any aspect of the user interface may be changed dynamically while an application executes. It also means that many interesting applications can be created without writing any new C code, simply by writing Tcl scripts for existing applications. Furthermore, Tk provides a special send command that allows any Tk-based application to invoke Tcl commands in any other Tk-b..