Distributed Systems: Difference between revisions
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Out of the many possible definitions of a distributed system, we herein employ the following, |
Out of the many possible definitions of a distributed system, we herein employ the following, |
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which is perhaps the most general (and in particular supercedes Lamport's humorous remark |
which is perhaps the most general (and in particular supercedes Lamport's humorous remark |
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that |
that ''a distributed system is the one that prevents you from working because of the failure of |
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a machine that you had never heard of |
a machine that you had never heard of''): |
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; Distributed System: |
; Distributed System: |
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The first implies that parts of the system, although they might be usable stand-alone, are |
The first implies that parts of the system, although they might be usable stand-alone, are |
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not what we mean by the term -- a cell-phone's games or calendar functions are not distributed, |
not what we mean by the term -- a cell-phone's games or calendar functions are not distributed, |
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but the service |
but the service ''communicate by voice independently of location'' is. |
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The second narrows down the range: programs on the same host and communicating over IPC are not |
The second narrows down the range: programs on the same host and communicating over IPC are not |
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considered distributed. |
considered distributed. |
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Revision as of 09:49, 1 December 2004
Introduction
Out of the many possible definitions of a distributed system, we herein employ the following, which is perhaps the most general (and in particular supercedes Lamport's humorous remark that a distributed system is the one that prevents you from working because of the failure of a machine that you had never heard of):
- Distributed System
A distributed system is comprised by a set of distributed (i.e., not located in the same spot) components (hardware and/or software) working together to provide one service.
That is, there are two characteristics to a distributed system: (1) the service it provides emerges at the system level and (2) components must communicate over links (which are components themselves). The first implies that parts of the system, although they might be usable stand-alone, are not what we mean by the term -- a cell-phone's games or calendar functions are not distributed, but the service communicate by voice independently of location is. The second narrows down the range: programs on the same host and communicating over IPC are not considered distributed.
Concurrency
Trust
Fault Tolerance
Distributed systems allow parts of the system to be located on separate computers and different locations. So business logic and data can be reached from any remote computer (location).
Distributed objects are the most recent development in distributed computing. Distributed object technologies such as Java RMI, CORBA, and DCOM allow objects running on one machine to be used by applications on different computers.