In archival systems, storage media are often replaced much earlier than their expected service life in exchange for other benefits of new media, such as higher capacity, bandwidth, and I/O operations per second, or lower costs. In an era of decreasing media density growth rates, retiring media early by considering only short-term benefits while discarding potential long-term cost benefits could have a negative long-term impact on an archival system's economics. To extend an archival system's life, at low cost, while limiting performance degradation, we suggest extending media lifetime past manufacturer recommendations as well as increasing the horizon for planning and provisioning future media purchases. We present a cost-benefit analysis of the impact of prolonged media usage and long-term planning. Through Monte Carlo simulation, we simulate the behavior of an archival system using tapes, hard disk drives (HDDs), solid state devices (SSDs), and Blu-ray discs. We show that leaving older media in the archival system makes economic sense for SSDs without significantly affecting reliability; we show cost improvements of approximately 10% for SSDs for a low annual media density growth rate, such as 5%, which would have been a loss of 35%, for a high annual media density rate, such as 20%. We show that, for SSDs and hard disks, the optimal planning time of an archival system is at least as long as the media service life. Combining prolonged media usage with an extended planning horizon reduced costs by 15% for a system using SSDs.

Emerging Web services, such as email, photo sharing, and web site archives, must preserve large volumes of quickly accessible data indefinitely into the future. The costs of doing so often determine whether the service is economically viable. We make the case that these applications' demands on large scale storage systems over long time horizons require us to reevaluate traditional system designs. We examine threats to long-lived data from an end-to-end perspective, taking into account not just hardware and software faults but also faults due to humans and organizations. We present a simple model of long-term storage failures that helps us reason about various strategies for addressing some of these threats. Using this model we show that the most important strategies for increasing the reliability of long-term storage are detecting latent faults quickly, automating fault repair to make it cheaper and faster, and increasing the independence of data replicas.

The LOCKSS project has developed and deployed in a world-wide test a peer-to-peer system for preserving access to journals and other archival information published on the Web. It consists of a large number of independent, low-cost, persistent Web caches that cooperate to detect and repair damage to their content by voting in “opinion polls.” Based on this experience, we present a design for and simulations of a novel protocol for voting in systems of this kind. It incorporates rate limitation and intrusion detection to ensure that even some very powerful adversaries attacking over many years have only a small probability of causing irrecoverable damage before being detected.

The LOCKSS project has developed and deployed in a world-wide test a peer-to-peer system for preserving access to journals and other archival information published on the Web. It consists of a large number of independent, low-cost, persistent web caches that cooperate to detect and repair damage to their content by voting in "opinion polls." Based on this experience, we present a design for and simulations of a novel protocol for voting in systems of this kind. It incorporates rate limitation and intrusion detection to ensure that even some very powerful adversaries attacking over many years have only a small probability of causing irrecoverable damage before being detected.

Abstract Only the diehards want to develop applications using basic window system facilities. The preferred approach is a higher‐level “toolkit” of user interface components, such as menus and scroll bars. Experience with current toolkits shows the need for an object‐oriented interface to these components. NeWS, the Network/extensible Window System, allows user interface components to be programmed in PostScript. Fortunately, object‐oriented interfaces are natural in PostScript, and they have been used to create a toolkit with some novel properties. Among these are the use of concurrent processing and run‐time inheritance of component methods. “Postscript is the future of words on paper.”Arthur C. Clarke

Abstract The input facilities of GKS, the draft international standard for 2‐D graphics software, are presented from an application programmer's viewpoint. The basic concepts are reviewed, concentrating on the differences between GKS and earlier systems. These input facilities can be used in three distinct styles. One provides high portability by sacrificing control over details of the user interface. Another can exploit hardware capabilities by sacrificing portability. A third can provide portability and control over the user interface, at the cost of extra application code. All three styles are described, and illustrated with skeleton applications.

A binding of GKS, the draft ISO standard for 2D graphics software, to the programming language C is presented, together with the principles underlying its design. The binding is compared with the binding to FORTRAN. An implementation of GKS according to this binding is also described, particular attention being paid to the techniques for segment storage, input, and workstations. The implementation is assessed against implementations in FORTRAN.

The concept of virtual input devices, enunciated by Wallace, has been the accepted basis for producing device-independent interactive graphics systems. It was used by GSPC for the Core System, and it underlies the draft international standard GKS.