04-10-2012, 12:02 PM
Distributed Systems
distribute computing.pdf (Size: 589.36 KB / Downloads: 34)
What is a Distributed System?
・A distributed system is a collection of independent computers that appears to its users as a single coherent system[Tanenbaumand van Steen]
・A distributed system is one in which hardware or software components located at networked computers communicate and coordinate their actions only by passing messages
・A distributed system is one that stops you getting work done when a machine you’ve never even heard of crashes
What is a Distributed System -2
“A distributed system is a system designed to supportthe development of applications and services which can exploita physical architecture consisting of multiple autonomousprocessing elements that do not share primary memorybut cooperate by sending asynchronousmessages over a communications network”
Why Distributed Systems?
Resource sharing
Availability
Extensibility
Improved performance
Structure of modern organisations
Pervasive nature of communications technologies
Examples of Distributed Systems
The Web
Shopping on-line e.g. Flights, buying a PC etc
Aircraft industry
Additional processing units are used for specific needs (data logging, cockpit displays, etc.)
Modern planes have replicated flight control computers (Airbus A330/A340 planes have 5 for instance)
Peer-to-Peer (P2P) file sharing networks
Each user contributes to the network
Auto-organisation, no centralised entity
What is CORBA? What does it do?
CORBAis the acronym for Common Object Request Broker Architecture, OMG's open, vendor-independent architecture and infrastructure that computer applications use to work together over networks. Using the standard protocol IIOP, a CORBA-based program from any vendor, on almost any computer, operating system, programming language, and network, can interoperate with a CORBA-based program from the same or another vendor, on almost any other computer, operating system, programming language, and network.
RPC and Transparency
RPC does succeed in providing a level of reasonable level of transparency
Programmers do not need to know the location of servers (location transparency)
They are not aware of the underlying engineering required to access the service (access transparency)
However, transparency is compromised by a number of key factors:
The performance of remote procedures will be significantly different from local calls
Parameter passing will be different, e.g. passing an address as a parameter
Other things can go wrong, e.g. network problems
distribute computing.pdf (Size: 589.36 KB / Downloads: 34)
What is a Distributed System?
・A distributed system is a collection of independent computers that appears to its users as a single coherent system[Tanenbaumand van Steen]
・A distributed system is one in which hardware or software components located at networked computers communicate and coordinate their actions only by passing messages
・A distributed system is one that stops you getting work done when a machine you’ve never even heard of crashes
What is a Distributed System -2
“A distributed system is a system designed to supportthe development of applications and services which can exploita physical architecture consisting of multiple autonomousprocessing elements that do not share primary memorybut cooperate by sending asynchronousmessages over a communications network”
Why Distributed Systems?
Resource sharing
Availability
Extensibility
Improved performance
Structure of modern organisations
Pervasive nature of communications technologies
Examples of Distributed Systems
The Web
Shopping on-line e.g. Flights, buying a PC etc
Aircraft industry
Additional processing units are used for specific needs (data logging, cockpit displays, etc.)
Modern planes have replicated flight control computers (Airbus A330/A340 planes have 5 for instance)
Peer-to-Peer (P2P) file sharing networks
Each user contributes to the network
Auto-organisation, no centralised entity
What is CORBA? What does it do?
CORBAis the acronym for Common Object Request Broker Architecture, OMG's open, vendor-independent architecture and infrastructure that computer applications use to work together over networks. Using the standard protocol IIOP, a CORBA-based program from any vendor, on almost any computer, operating system, programming language, and network, can interoperate with a CORBA-based program from the same or another vendor, on almost any other computer, operating system, programming language, and network.
RPC and Transparency
RPC does succeed in providing a level of reasonable level of transparency
Programmers do not need to know the location of servers (location transparency)
They are not aware of the underlying engineering required to access the service (access transparency)
However, transparency is compromised by a number of key factors:
The performance of remote procedures will be significantly different from local calls
Parameter passing will be different, e.g. passing an address as a parameter
Other things can go wrong, e.g. network problems