CPE 633
Chapter 1 - Preliminaries
Dr. Rhonda Kay Gaede
UAH
1
Electrical and Computer Engineering
UAH Chapter 1 CPE 633
Motivation
• Computers are everywhere.
• Computers are used in _______________
and _________________ applications.
• Computer systems (______________ and
____________) are incredibly __________.
• With complexity comes a propensity
for ____________.
• Two approaches:
– ________________________
– ____________________________________________
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Electrical and Computer Engineering
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UAH Chapter 1 CPE 633
1.1 Fault Classification
• Definitions
– A fault (or failure) can be either a
___________________ or a ___________________
– An ______ is a manifestation of the ______.
• Examples
– Output of adder circuit ______________
– sin(x) computation really ___________
• Fault effects can ____________.
• To limit this spread, designers
incorporate _________________________.
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Electrical and Computer Engineering
UAH Chapter 1 CPE 633
1.1 Fault Classification
• These containment zones are
__________ that reduce the chance
that an effect can spread.
– ____________________________________________
_______.
• Hardware faults can be:
– ________________
– _____________
– __________________
• Hardware faults are __________ or
_______________.
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Electrical and Computer Engineering
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UAH Chapter 1 CPE 633
1.2 Types of Redundancy
• All of fault tolerance is an exercise
in _____________ and ____________
_________________ – the property of
___________________________ than is
minimally necessary.
• Four forms of redundancy: __________,
_____________, _________, ______________
• Hardware redundancy is provided by
___________________________ in the
design to _________ or _________ errors.
– It can be ________, _________ or __________.
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Electrical and Computer Engineering
UAH Chapter 1 CPE 633
1.2 Types of Redundancy
• The best-known form of _____________
redundancy, _________________ and
_______________ coding, is widely used in
___________________________.
• ___________________ and ________________
codes are also used to protect data
communicated over _________ (channels
subject to many __________ failures)
channels. ______________ upon detection of
an error is ________ redundancy.
• _______________ redundancy leads to
hardware _____________.
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Electrical and Computer Engineering
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UAH Chapter 1 CPE 633
1.3 Basic Measures of Fault Tolerance
• What does it mean to make machines more
__________________?
– We need __________
• Traditional Measures
– ______________, _____, is the probability that the
system has been ___________________ in the time
interval [0,t]. It is suitable for applications in
which even a ___________________________ can prove
costly.
• ____________________________ (MTTF)
• _______________________________ (MTBF)
• _______________________ (MTTR)
• ________ = ________ + ___________
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Electrical and Computer Engineering
UAH Chapter 1 CPE 633
1.3 Basic Measures of Fault Tolerance
– _______________, _____, is the average _____________
_______ over the interval [0.t] that the system is
_____.
A = lim A(t )
t →∞
MTTF MTTF
A= =
MTBF MTTF + MTTR
– ________________________, ______, is the probability
that the system is up at ___________________________
____________.
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Electrical and Computer Engineering
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UAH Chapter 1 CPE 633
1.3 Basic Measures of Fault Tolerance
• All this is nice as long as we know what ____ means.
– Some cases are simple, _________________ for example.
– Other cases not so much, what if ______________________
____________________________________________?
– Many systems have ________________ states
• Extension of traditional measures to _____________
___________________________________ of a system with n
processors.
n
ACC = ∑ ci Pi (t )
i =1
• Ci is the _______________________________ of a system with I
____________________ processors
• Pi(t) is the probability that exactly __________________ are
operational at time t
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Electrical and Computer Engineering
UAH Chapter 1 CPE 633
1.3 Basic Measures of Fault Tolerance
• Network Measures
– Classical _______ and ____________________ – the minimum
number of ___________ and __________ that have to fail
before the network becomes ________________________.
– Average ________________________
– Maximum __________________ (_______________)
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Electrical and Computer Engineering
