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Comparison between Shared memory architecture and Shared nothing architecture



Shared-Memory Architecture:






This architecture connects different processor under one operating system through high speed interconnections (cross-bar switch or high speed bus etc). Query response time is reduced by dividing workload to any connected processor with least or no workload. This architecture provides two main advantages over other architectures as it manages load in a perfect manner and easy to manage. It uses least busy processors and allocates new tasks to it so that query processing is done at a fast speed.










But along with two major advantages it has three basic disadvantages too. These are low availability, any fault or problem may affect most of the processors making less availability, high cost to link processors and third, limited extensible.



















Performance

  Shared memory architecture provides a good performance as compared to shared nothing architecture by balancing query load on a processor with less or no work load.


Software complexity query processing





 

There is a need to parallelize intra query but it remains simple. Load balancing can be easily achieved at run time processing with this architecture by assigning new tasks to nodes with less load or no load.






Availability

 
Shared memory has disadvantage over shared nothing architecture that it has low availability, any fault or problem may affect most of the processors making less availability. Duplex memory with a repeating interconnection is a solution to this problem.


Shared nothing architecture 


Performance



This architecture provides a complexity to manage load caused by required distributed database functions to be implemented for a large number of nodes

Software complexity query processing 

Load balancing in this architecture is comparably complex as it needs to decide load balancing on the basis of data placed at different locations. With the addition of new nodes, there is a need to reorganize database for load balancing issue.

Availability

Shared nothing architecture is good as compared to shared memory architecture as it provides high availability by copying data on many nodes.
Any fault or disturbance in any node may not disturb the availability to the data 




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