ReliabilityAndy Jensen

Sandy Cabadas

Understanding Reliability and its issues can help one solve them in relatable areas of computing

Thesis

What is Reliability?

Understanding differences between similar terms

Challenges of Reliability & How to Solve Them

Topics Impacted by Reliability

Outline

Reliability is the capability of a person or system to be able to perform and maintain its functions in any scenario given

The capacity of a designed, produced or maintained item to perform as required over time

The resistance to failure of an item over time

Reliability

Tries to avoid: Anything going wrong Inconsistencies

Tries to accomplish Meeting requirements Convenience

Reliability

Reliability is a process of many Just a few…

Systems Computer networks Data Engineering

Dependents

What is Reliability?

Understanding differences between similar terms

Challenges of Reliability & How to Solve Them

Topics Impacted by Reliability

Outline

Reliability Expected time until incorrect service System to perform and maintain its functions in routine

circumstances, as well as hostile or unexpected circumstances. Availability

% of time delivering correct service Stability

 the quality of being enduring and free from change or variation

Dependability Measure of systems reliability, availability, and maintenance

support

Understanding the Differences

Validity: Measuring what a system is supposed to do

Reliability: Getting the same results every time for a certain test

Reliability doesn’t matter if the test isn’t valid

Reliability and Validity

Reliability and Validity

What is Reliability?

Understanding differences between similar terms

Challenges of Reliability & How to Solve Them

Topics Impacted by Reliability

Outline

Planning systems for reliability Analyzing systems for reliability Designing systems for reliability Implementing systems for reliability Reliability engineering Complexity Simulation for testing reliability

Tools to simulate What to test How to determine the results What to do after

Challenges of Reliability

Constraints Redundancy and error recovery mechanisms

are required May require new features

Rigorously verified to ensure their correct implementation

Challenges of Reliability

System Type Unavailability Reliability Class(9’s)

(min/year) (%)Unmanaged 52,560 90% 1Managed 5,256 99% 2Well-Managed 526 99.9% 3Fault-tolerant 53 99.99% 4High-reliability 5 99.999% 5Very-highly reliable 0.5 99.9999% 6Ultra-highly reliable 0.05 99.99999% 7

Reliability Classes

A measure of trust of results produced by a system

Idea and concept is there and all there is to it is recognizing the situation and knowing that it has to be reliable. Sufficient for use User satisfaction Meet standards of reliability

System Reliability

To achieve system reliability Make sure the components of the system are

constructed properly Make sure that any failure or anything that is

detected to be wrong be taken care of and fixed

Solving System Reliability

User plays a specific role and that is being a tester and judging the system and how reliable it is Knowledge Experience

Inexperienced user will not be able to determine reliability, the wrong in a hardware or system Unreliable source Challenging to find users that are going to

determine reliability of a system

User Reliability

Developers have to keep in mind all types of users. Novice Users: Intermediate Users Expert Users

Developer have to keep in mind user will sacrifice software efficiency when the price is right for them. Sometimes the issue with having a good server is that today

to have a cost efficient server sometimes means using systems of less quality and so the reliability suffers there

To solve: Not focusing on the cost. To solve: Understanding point of view of the users and

dedication of the developer.

User Reliability

System designer detects and corrects errors User is open minded about the designers updates For example in software:

Free of bugs and software correctly written. Software bugs are frequently seen in both software

and hardware. When a software system get to where it is

considered highly reliable then it has been examined to where the system is close to no errors in the software.

Solving User Reliability

What is Reliability?

Understanding differences between similar terms

Challenges of Reliability & How to Solve Them

Topics Impacted by Reliability

Outline

Large Impact Measured by the frequency of failure, the

time it takes to recover from a failure, and the network’s robustness in a catastrophe

Ensuring that each segment that the source sends arrives at its destination

Reliable protocols > delivery of data Networking outages > still needs to be

reliable

Reliability in Networking

Large Impact Hard to face for OS designers &

implementers Wide variety of environments Many different users relying on OS

Reliability in Operating Systems

Large Impact Database Performance

requested information is always correctly and reliably stored and accessed

Reliability in Databases

Data Redundancy Occurs in databases when a field is repeated in

2+ tables Customer data attached to each product bought

Same data

Data redundancy can prevent data reliability

Data Reliability

Questions?