1. NADAR SARASWATHI COLLEGE OF ARTS AND SCIENCE,THENI.
DEPARTMENT OF COMPUTER SCIENCE.
REABILITY AND FAULT TOLERANCE
BY:
B.POORANI
I-MSC(CS)
2. FAULT TOLERANCE:
The fault tolerance is the property that enables a system to continue
operating properly in the event of the failure of one or more faults
within some of its component .
If its operating quality decrease at all, the decrease is proportional to
severity of the failure , as compared to a naively designed system, in
which even a small failure can cause total breakdown.
Fault tolerance is particularly sought after in high –availability,
mission – critical, or even life-critical systems.
3. Research into the kind of tolerances needed for critical system
involves a large amount of interdisciplinary work. The more
complex the system, the more carefully all possible interaction have
to be considered and prepared for.
Considering the importance of high-value system in transport ,
public utilities and the military, the fields of topic that touch on
research is very wide.
4. REPLICATION:
Providing multiple identical instances of the same system or subsystem, directing
tasks or request to all of them in parallel, and choosing the correct results on the
basis of a quorum.
REDUNDANCY:
Providing multiple identical instances of the same system and switching to one of
the remaining instances in case of a failure.
DIVERSITY:
Providing multiple different implementation of the same specification and
Using them like replicated system to cope with error in a specific implementation.
5. BIST:
BIST stands for built In self test. system carrier out the test of itself
after a certain period of time again and again , that is BIST
techniques for hardware fault-tolerance.
When system detects a fault it switches out the faulty component
and switched in the redundant of it, system basically reconfigure
itself in case of fault occurrence.
6. TMR:
TMR is a triple modular redundancy .three redundant copies of
critical components are generated and all these three copies are run
concurrently.
Voting of results of all redundant copies are done and majority result
is selected . It can tolerate the occurrence of a single fault at a time.
7. SOFTWARE FAULT-TOLERANCE
TECHNIQUES:
Software fault-tolerance techniques are used to make the software
reliable in the condition of fault occurrence and failure.
There are three techniques used in the software fault-tolerance .
N-version programming
Recovery blocks
Check-pointing and rollback recovery
