22-03-2014, 04:09 PM
DISTRIBUTED SYSTEMS
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What is a Distributed System?
A distributed system is a collection of autonomous
computers linked by a computer network that appear to
the users of the system as a single computer.
Some comments:
• System architecture: the machines are
autonomous; this means they are computers which,
in principle, could work independently;
• The user’s perception: the distributed system is
perceived as a single system solving a certain
problem (even though, in reality, we have several
computers placed in different locations).
Availability
If machines go down, the system should work
with the reduced amount of resources.
• There should be a very small number of critical
resources;
critical resources: resources which have to be up in
order the distributed system to work.
• Key pieces of hardware and software (critical
resources) should be replicated ⇒ if one of them
fails another one takes up - redundancy.