Process resilience ! Fault tolerance is required where there are high availability requirements or where system failure costs are very high. Recovery . Thisreport isan introduction to fault-tolerance concepts and systems, mainly from the hardware point of view. Maintainability . Software fault is also known as defect, arises when the expected result don't match with the actual results. software faults. 4. If its operating quality decreases at all, the decrease is proportional to the severity of the failure, as compared to a naively designed system, in which even a small failure can cause total breakdown. •Validation testing Intended to show that the software is what the customer wants (Basically, there should be a test case for every requirement.) Abstract. Pages 205-241. This new title in Wiley’s prestigious Series in Software Design Patterns presents proven techniques to achieve patterns for fault tolerant software. Static techniques use the concept of fault masking. An introduction to the terminology is given, and different ways of achieving fault-tolerance with redundancy is studied. Fault tolerance is a major concern to guarantee availability and reliability of critical services as well as application execution. Fault-Tolerant Systems is the first book on fault tolerance design with a systems approach to both hardware and software. – E.g., a software bug in a subroutine is not visible if the subroutine is not called 3 Types of Failures 4 also known as Byzantine failures. (also called passive redundancy or fault-masking) Dynamic techniques achieve fault tolerance by detecting the existence of faults and performing some Likewise, given two single­qubit encoded states, one can perform CNOT operations between the kth qubit of one set, with the kth qubit of the other. – Incorrect implementation of requirements. the software with test data to discover program defects. Fault Tolerance Computing-- Draft Carnegie Mellon University 18-849b Dependable Embedded Systems Spring 1999 . No other text on the market takes this approach, nor offers the comprehensive and up-to-date treatment that Koren and Krishna provide. In order to minimize failure impact on the ... Software Rejuvenation-It is a technique that designs the system for periodic reboots. Software fault tolerant. Reliable group communication ! (h) Partitioning methods and means of preventing partitioning breaches. software fault-tolerance). It can also be error, flaw, failure, or fault in a computer program. This helps the enterprises to evaluate their infrastructure needs and requirements, and provide services when the associated devices are unavailable due to some cause. 3.4 Fault Tolerance of CNOT Gate The σ x, σ z, and H gates can all be performed on a single encoded qubit with fault­tolerance because these gates are always applied to single qubits. • Basic concepts in fault tolerance • Masking failure by redundancy • Process resilience • Reliable communication – One-one communication – One-many communication • Distributed commit – Two phase commit • Failure recovery – Checkpointing – Message … Software Development: DO-178B (g) Design methods and details for their implementation, for example, software data loading, user modifiable software, or multiple-version dissimilar software. •Defect testing Intended to reveal defects • (Defect) Testing is... • fault … How to efficiently design a future-proof software architecture of a new product using non-functional requirements analysis and software quality attributes Software Fault Tolerance. • Roughly speaking, fault tolerance means “able to continue operation in spite of Distributed commit ! Fault tolerance ! Software redundancy Lecture set 5A in .ppt; Lecture set 5A in pdf (six slides per page) Variuos fault tolerant measures Lecture set 5B in .ppt The root cause of software design errors is the complexity of the systems. When the first‐pass adjudicator fails, the second‐pass adjudicator, which is backward recovery, is executed. Availability, Robustness, Fault Tolerance and Reliability: A robust software should not lose its availabilty even in most failure states. Ying Shi. e.g. What is J1939? Fault Tolerance • It is not enough for reliable systems to avoid faults, they must be able to tolerate faults. – New : Techniques for dealing with common types of faults in parallel programs Besides, even if whole application crashes, it may recover itself using backup hardware and data with fault tolerance approaches. Safety ! Availability ! Part15: Software fault Tolerance II Subject: Fault Tolerant Computing Author: I. Koren Last modified by: krishna Created Date: 8/12/1995 11:37:26 AM Document … Software based fault detection - Tim Prince: PPT: Self Recovery of Server Programs - Chesta Dwivedi: PPT: Dynamic Fault Trees - Ashok Aditya: PPT: Device Failure Tolerance Using Software - Haribabu Narayanan: PPT: FPGA Fault Tolerance - Matt Clausman: PPT: Byzantine Storage - Debkanta Chakraborty : PPT : Spring 2009 Student Presentations Object-based fault tolerance allows programmers to implement fault tolerance in their applications without having to master all the details of the discipline. Even if some components are broken down, it may continue running. (i) Descriptions of the software components, whether they are new or Software Fault Tolerance: A Tutorial Because of our present inability to produce error-free software, software fault tolerance is and will continue to be an important consideration in software systems. Previously, the course had been taught primarily by Dr. John Kelly, who instituted the two-course sequence ECE 257A/B, the first covering general topics and the second (now discontinued) devoted to his research focus on software fault tolerance. The paper is a tutorial on fault-tolerance by replication in distributed systems. 2/18 Concepts in fault tolerance (contd.) Some software fault‐tolerance techniques can be used for both forward and backward recovery ‐ for example, TPA. Introduction. Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of (or one or more faults within) some of its components. Kangasharju: Distributed Systems 3 Basic Concepts Dependability includes ! Reliability ! Simma Software, Inc. Fault tolerance is a concept used in many fields, but it is particularly important to data storage and information technology infrastructure. Most bugs arise from mistakes and errors made by developers, architects. This is a key reference for experts seeking to select a technique appropriate for a given system. Relies on voting mechanisms. n Computer-based systems have increased dramatically in scope, complexity, and pervasiveness n Safe and reliable software operation is a significant requirement for many systems n Aircraft, medical devices, nuclear safety, electronic banking and commerce, automobiles, etc, … • Faults occur for many reasons: – Incorrect requirements. Fault Types. These techniques are designed to achieve fault tolerance without requiring any action on the part of the system. Cloud computing is a large-scale and complex distributed computing paradigm where the configurable resources (servers, storage, network, data and software applications) are provided as multi-level services via virtualization technologies. Abstract: As users are not concerned only about whether it is working but also whether it is working correctly, particularly in safety critical cases, Fault Tolerant Computing (FTC) plays a important role especially since early fifties. Software patterns have revolutionized the way developer’s and architects think about how software is designed, built and documented. fault in floating-point unit: switch to software emulation Bräunl 2003 23 Objectives of Fault Tolerance [Johnson] • Maintainability M(t) probability that a failed system will be restored to an operational state within period of time t. The most important point of it is to keep the system functioning even if any of its part goes off or faulty [18]-[20]. 1. Explicating Fault Tolerance in Cloud Computing. S/W Fault-Tolerance – Ebnenasir – Spring 2009 Course Outline – Cont’d • Fault tolerance – Techniques for the validation and verification of fault-tolerance (e.g., fault injection and model checking of fault-tolerance). Fault tolerance means that the system can continue in operation in spite of software failure. Fault Tolerance Systems Fault tolerance system is a vital issue in distributed computing; it keeps the system in a working condition in subject to failure. Why software fault tolerance? During each adjudicator, the voting process used is typical forward recovery. Contact • E-mail: jrsimma “at” simmasoftware “dot” com ... J1939 specification is 6.5MB, this PPT is 225KB. It restarts the system with clean state [5]. Software fault-tolerance: 3: N-version programming, recovery blocks, robust data structures and process pairs: Modeling and Evaluation – 3: 2: Fault-injection: techniques and tools, Formal methods: Parallel and Distributed systems: 4: Check-pointing and recovery, Byzantine fault-tolerance and paxos: Case Studies: 2: Stratus and AT&T systems For a system to be fault tolerant, it is related to dependable systems. Fault tolerance in cloud computing is about designing a blueprint for continuing the ongoing work whenever a few parts are down or unavailable. – Unforeseen situations. Knowledge of software fault-tolerance is important, so an introduction to software fault-tolerance is also given. Lee, Peter Alan (et al.) Fault-tolerance is the ability of a system to maintain its functionality, even in the presence of faults. Homework 1: 1.13, 1.14, 1.17 (3 examples) Fault Tolerance & Reliability CDA 5140 Spring 2006 Chapter 1 Overview & Definitions Topics basic concepts of Fault Tolerance (FT) reliability & availability of systems, both hardware & software tools to compare & contrast FT designs What is FT? multiprocessor: run with 1 PE less e.g.