We solve for the availability of an n-processor VAXcluster system using a hierarchical approach that allows us to: 1) obtain a closed-form answer to an apparently difficult problem, and 2) determine the optimal number of processors in the cluster for a given set of cluster parameters. Our novel approach is a 2-level hierarchical model in which the lower-level model is a 9-state Markov chain tha...

IT service availability is at the core of customer satisfaction and business success for today’s organisations. Many medium-large size organisations outsource part of their IT services to external providers, with Service Level Agreements describing the agreed availability of outsourced service components. Availability management of partially outsourced IT services is a non trivial task since cl...

this research was conducted during 2009 at a regional scale in birjand and qaen counties, southern khorasan, as an attempt to develop a sustainability index (si) for quantifying the sustainability of saffron agroecosystem. the information of these agroecosystems, including socio-economic, agronomic and ecological indicators was collected using questionnaires and was subjected to statistical ana...

Information technology (IT) service availability is at the core of customer satisfaction and business success for today’s organisations. Many medium‐ to large‐size organisations outsource part of their IT services to external providers, with service‐level agreements describing the agreed availability of outsourced service components. Availability management of partially outsourced IT services i...

In this paper, the authors have focused on the stochastic analysis of an internet data center (IDC), which consists of a database main server connected to a redundant server. Observing the different possibilities of functioning of the system, analysis has been done to evaluate the various reliability characteristics of the system. The system can completely fail due to failure of redundant serve...

Confronted to the increasing dynamic of Internet routing system and its underlying topology, we propose a reliability and availability analysis method based on the characterization of the dynamic properties (in particular, the stability properties) of routing paths and their corresponding forwarding paths. The key driver underlying this method is that transient but frequent changes in the spati...

Availability analysis is used to assess the possible failures and their restoration process for a given system. This analysis involves the calculation of instantaneous and steady-state availabilities of the individual system components and the usage of this information along with the commonly used availability modeling techniques, such as Availability Block Diagrams (ABD) and Fault Trees (FTs) ...

As modern society becomes more and more dependent on computers and computer networks, vulnerability and downtime of these systems will significantly impact daily life from both social and economic point of view. Words like reliability and downtime are frequently heard on radio and television and read in newspapers and magazines. Thus reliability and availability have become popular terms. Howev...

The most common aim in designing a survivable network is to achieve restorability against all single span failures, with a minimal investment in spare capacity. This leaves dual-failure situations as the main factor to consider in quantifying how the availability of services benefit from the investment in restorability. We approach the question in part with a theoretical framework and in part w...

This paper describes a set of MATLAB functions currently being developed for SBAS availability analysis. This toolset includes simulation algorithms that are constantly being developed and updated by various working groups. This set of functions is intended for use as a fast, accurate, and highly customizable experimental test bed for algorithm development. A user-friendly interface has also be...