abhishekgahlot · May 7, 2017 21:37
diff --git a/CAP-Theorem b/CAP-Theorem
 CAP - Consistency, Availability and Partition-Tolerant

 The CAP principle states that in distributed computing when it comes
 to consistency (C), availability (A) and partition (P)
 resilience/tolerance you can have only two of the three.

 I was recently introduced to this principle and find it rather
 insightful.  Basically you can't have your cake and eat it too,
 otherwise (computing) life would be too easy.

 Eric Brewer, a University of California, Berkeley professor and the
 co-founder and Chief Scientist of Inktomi, in a 2000 Principles of
 Distributed Computing (PODC) talk, stated it was impossible for
 distributed web services to guarantee consistency, availability and
 partition-tolerance.

 Consistency.  Think database consistency.  A read after an update
 should reflect the update.

 Availability.  Highly available web services mean every requests
 should succeed and receive a response.

 Partition-tolerance.  This arise out of the desire for
 fault-tolerance.  The service should be able to function when part of
 network fails, when a partition between data replicas will still allow
 the service to operate.

 Take, for example, the Amazon S3 service (Simple Storage Service).
 Users can upload data to Amazon, much like a simple FTP service, with
 very high availability and scalability.

 Amazon's S3 guarantees availability and partition-tolerance but does
 not guarantee consistency.  Data is replicated to many data centers,
 and requests will continue to succeed even if communication between
 data centers fail.  However, it is possible that after an upload a
 download on a different node would fail, because the data has not been
 replicated to that node.  The service is not consistent.  Amazon
 describes this as eventually consistent model.

 On the other hand, take a service with distributed transactions.  It
 will be consistent and available, but if the network partitions the
 service will not function.

 Reference: Brewer's Conjecture and the Feasibility of Consistent,
 Available, Partition-Tolerant Web Services, Seth Gilbert and Nancy
 Lynch.

 More infos, http://en.wikipedia.org/wiki/CAP_theorem
	CAP - Consistency, Availability and Partition-Tolerant

	The CAP principle states that in distributed computing when it comes
	to consistency (C), availability (A) and partition (P)
	resilience/tolerance you can have only two of the three.

	I was recently introduced to this principle and find it rather
	insightful. Basically you can't have your cake and eat it too,
	otherwise (computing) life would be too easy.

	Eric Brewer, a University of California, Berkeley professor and the
	co-founder and Chief Scientist of Inktomi, in a 2000 Principles of
	Distributed Computing (PODC) talk, stated it was impossible for
	distributed web services to guarantee consistency, availability and
	partition-tolerance.

	Consistency. Think database consistency. A read after an update
	should reflect the update.

	Availability. Highly available web services mean every requests
	should succeed and receive a response.

	Partition-tolerance. This arise out of the desire for
	fault-tolerance. The service should be able to function when part of
	network fails, when a partition between data replicas will still allow
	the service to operate.

	Take, for example, the Amazon S3 service (Simple Storage Service).
	Users can upload data to Amazon, much like a simple FTP service, with
	very high availability and scalability.

	Amazon's S3 guarantees availability and partition-tolerance but does
	not guarantee consistency. Data is replicated to many data centers,
	and requests will continue to succeed even if communication between
	data centers fail. However, it is possible that after an upload a
	download on a different node would fail, because the data has not been
	replicated to that node. The service is not consistent. Amazon
	describes this as eventually consistent model.

	On the other hand, take a service with distributed transactions. It
	will be consistent and available, but if the network partitions the
	service will not function.

	Reference: Brewer's Conjecture and the Feasibility of Consistent,
	Available, Partition-Tolerant Web Services, Seth Gilbert and Nancy
	Lynch.

	More infos, http://en.wikipedia.org/wiki/CAP_theorem