1 / 17

Fault Tolerance Fundamentals

Fault Tolerance Fundamentals . ITV Model-based Analysis and Design of Embedded Software Techniques and methods for Critical Software Anders P. Ravn Aalborg University August 2011. Fault Tolerance. Means to isolate component faults. Prevents system failures.

lynna
Télécharger la présentation

Fault Tolerance Fundamentals

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fault Tolerance Fundamentals ITV Model-based Analysis and Design of Embedded Software Techniques and methods for Critical Software Anders P. Ravn Aalborg University August 2011

  2. Fault Tolerance Means to isolate componentfaults Prevents systemfailures May increase systemdependability

  3. Dependability - attributes • Availability • Reliability • Safety • Confidentiality • Integrity • Maintainability

  4. Dependability - impairments • Faults • Errors • Failures

  5. System and Component

  6. Propagation among Components

  7. Error Classification (Fault  Error) • Effect • Extent • latent • effective • local • distributed

  8. Failure Classification (Fault  Error  Failure) • Consequence • benign • malign (a mishap)

  9. Fault Tolerance Means to isolate componentfaults ... And mask them Prevents systemfailures May increase systemdependability

  10. Fault Tolerance

  11. Full tolerance • Graceful Degradation • Fail safe FT - levels BW p. 107

  12. Retry ... ... Try Try Try FT basis: Redundancy • Time • Space Try Retry BW p. 109

  13. Fault Tolerance

  14. Basic Strategies

  15. Failure exception Interface exception Request/response Interface exception Failure exception Request/response The ideal FT-component Normal mode Exception Handler

  16. Model Design Procedure • Model the correct component and check that it has the desired properties. • Model relevant faults and introduce them as internal transitions to error states. Check that this fault-affected. • Introduce into the model the mechanisms for fault detection, error recovery and masking and check that the desired properties are valid for this design.

  17. Exercise • What is the purpose of a watchdog-timer? • How could it be used in a space based redundancy scheme? • - in a time based redundancy scheme?

More Related