CAP theorem (Brewer’s theorem) :
It is impossible for distributed computer system to simultaneously provide all three of the following guarantees:
Consistency: There are many way to describe it
* All nodes see the same data at the same time.
* Once a state is stored in the system, it will report the same state in every subsequent operation until the state is explicitly changed by something outside the system.
* A service that is consistent operates fully or not at all.
* In other way to say, atomic-ness is built-in to service.
Availability:
* The degree to which a system is operable and in a committable state at the start of a mission, when the mission is called for at random
* Node failures do not prevent survivors from continuing to operate
Partition Tolerance:
* The system continues to operate despite arbitrary message loss
* No set of failures less than total network failure is allowed to cause the system to respond incorrectly
In other words, though it is very desirable to have Consistency, Availability and Partition-tolerance in distributed system, unfortunately
no distributed system can achieve all three at the same time!
Pity!
Here is quote from paper published by Seth Lloyd of MIT in 2001.
“Merely by existing, all physical systems register information. And by evolving dynamically in time, they transform and process that information. The laws of physics determine the amount of information that a physical system can register (number of bits) and the number of elementary logic operations that a system can perform (number of ops). The universe is a physical system. This paper quantifies the amount of information that the universe can register and the number of elementary operations that it can have performed over its history. The universe can have performed no more than 10^120 ops on 10^90 bits.”
Enjoy!
* Good communication
* Good sharing of tangible and intangible resources
* Learning from own and other team member’s mistake
* Good leader
* Enough resources to work with
* Good Commitment level
* Openness in environment
1. Eliminate waste
2. Minimize inventory
3. Maximize flow
4. Pull production from customer demand
5. Meet customer requirements
6. Do it right the first time
7. Empower workers
8. Design for rapid changeover
9. Partner with suppliers
10. Create a culture of continuous improvement
There are many ways:
Normative abnormality
We go by ‘Nothing is normal as nothing is perfect.’
Only perfect is 100% normal. Farther you are from ideal, more abnormal you are.
Clinical abnormality
When things are beyond certain level of irrationality, bizarreness, poor adapatation, unorganization, ineffectiveness.
Cultural abnormality
When things not considered ‘normal’ by a culture.
Statistical abnormality
This one is based on idea of normal distribution or bell curve. In mathematical normal distribution, 97% data points are within 30% difference from average value. So, if average is 100 for some data set, anything less than 70 and more than 130 should be abnormal. Farther away you are from average, more abnormal you are.
Subjective abnormality
People like (based on some criteria selected by me) me are more normal. People different from me are abnormal. I select criteria of abnormality.
