ReliabilityReliability

and

SHARPESHARPE

Outline

1. What is Reliability?

2. How can you evaluate it?

3. What is SHARPE?

4. Usage of SHARPE

What is Reliability?

• how long a system is continuously operational

• ability to function correctly over a specified period of time

Why is it so important?

• if system is unreliable, suffer a great loss

• affect the performance

• no system is perfect, so we need to evaluate how reliable of it and make improvement

Types of reliability

For a computer system, we can define 2 types:

• Hardware reliability

• Software reliability

How can you evaluate it?

• simulation model

- program whose execution mimics the dynamic behavior or the modeled system

• analytic model

- Make a mathematical prediction of the system reliability

Simulation

Advantages:

• predict system behavior without having to build and measure a system

Disadvantages:

• time consuming

What is SHARPE?

• Symbolic Hierarchical Automated Reliability and Performance Evaluator

• allows users to construct and analyze performance, reliability, availability and performability models

Advantages

• once set up the model, it can obtain the information easily and quickly

• easy to carry out sensitivity analysis

• not time-consuming

• easy to write the input file

How to use?

• After building the analytic model, then write a input file for the model

• input file contains:

- state the model type

- describe the system

- analyze the result

Example

Below is the reliability block diagram of a system consisting 8 components:

A B

C

C

C

D

D

E

Input file 1 block block1a 2 comp A exp(0.05) 3 comp B exp(0.01) 4 comp C exp(0.3) 5 comp D exp(0.25) 6 comp E exp(0.1) 7 parallel threeC C C C 8 parallel twoD D D 9 series sys1 A B threeC twoD E10 end1112 cdf(block1a)13 expr value(10; block1a)14 end

Analysis

• After an input file is ready, run the SHARPE and it will produce the result

• carry out sensitivity analysis

• by changing different mean to failure rate, you can obtain different combinations of result

How does it link to my research?

• in my research, SHARPE is used to analyze the reliability of network-centric environment

• with different combinations of probability function, compared with the traditional computing environment