12 - CriticalSystems

12 - CriticalSystems - CO502 Advanced Computer Architecture...

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CO502 – Advanced Computer Architecture Computer Architecture & ependability Dependability Roshan Ragel – Department of Computer Engineering Background – Critical Systems ased on: hn Rushby, ritical System Properties: Based on: John Rushby, Critical System Properties: Survey and Taxonomy , Reliability Engineering and System Safety , 43 (1994) pp 189-219 Critical System t There is a lot of disagreement concerning the definition of a “critical system”. t There are FOUR different views on the subject: 1. Dependability Approach 2. Safety Approach 3. Security Approach 4. Real Time Systems Approach t There are differing views on the relationship between properties and the compatibility of techniques from these approaches. Dependability Approach Safety Approach Security Approach Real Time Systems Approach
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t Introduced by Jean Claude Laprie t A dependable system is one for which the reliance may justifiably be placed on both its “ correctness ” and continuity of its delivery t “correctness” pertains to the conformity with requirements, specifications, etc. t “Dependability” encapsulates the technical meaning of terms such as reliability, safety, survivability, security and fault tolerance. Failure vs. Fault? t Failure is defined as the inability to provide a required service from the system because of faults . ilure roperty f e ternal ehavior f t Failure is a property of the external behavior of a system. t Failures can be either: t Benign t The consequences of failure = Benefits provided by ormal peration normal operation t Catastrophic t The consequences of failure >> Benefits provided by normal operation Failure and Internal States of a System t Suppose a system progresses through a set of states S 1 , S 2 , S 3 ,………S N S 1 S 3 S 4 S N S 2 Failure Occurs Fault Activated Latent Error Fault Tolerant System t The error or fault is latent from the state of activation until it manifests itself in the effective fault ate state. t
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This note was uploaded on 01/21/2012 for the course CSCI 593 taught by Professor Hamnes during the Spring '11 term at St. Cloud.

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12 - CriticalSystems - CO502 Advanced Computer Architecture...

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