Synonyms
Distributed architecture
Definition
In the shared-nothing architecture, each node is made of processor, main memory and disk and communicates with other nodes through the interconnection network. Each node is under the control of its own copy of the operating system and thus can be viewed as a local site (with its own database and software) in a distributed database system. Therefore, most solutions designed for distributed databases such as database fragmentation (called partitioning in parallel databases), distributed transaction management and distributed query processing may be reused.
Key Points
As opposed to symmetric multiprocessor (SMP), shared-nothing is often called massively parallel processor (MPP). Many research prototypes and commercial products have adopted the shared-nothing architecture because it has the best scalability. The first major parallel DBMS product was Teradata which could accommodate a thousand processors in its early version in the 1980s. Other major DBMS vendors, except Oracle, have provided shared-nothing implementations.
Shared-nothing has three main advantages: low cost, high extensibility, and high availability.
The cost advantage is better than that of shared-disk which requires a special interconnection network for the disks. By easing the smooth incremental growth of the system by the addition of new nodes, extensibility can be better (in the thousands of nodes). With careful partitioning of the data on multiple disks, almost linear speedup and linear scale up could be achieved for simple workloads. Finally, by replicating data on multiple nodes, high availability can be also achieved.
However, shared-nothing is much more complex than either shared-memory or shared-disk.
Higher complexity is due to the necessary implementation of distributed database functions for large numbers of nodes, in particular, data placement. Load balancing is more difficult to achieve because it relies on the effectiveness of database partitioning. Unlike shared-memory and shared-disk, load balancing is decided based on data location and not the actual load of the system. Furthermore, the addition of new nodes in the system presumably requires reorganizing the database to deal with the load balancing issues.
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Valduriez, P. (2018). Shared-Nothing Architecture. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_1512
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DOI: https://doi.org/10.1007/978-1-4614-8265-9_1512
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