Master-Slave Replication
Master-Slave Replication is a widely used replication model in databases where one database server (the 'master') replicates changes to one or more database servers (the 'slaves'). Key characteristics include:
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Unidirectional asynchronous replication: Data flows unidirectionally from the master server to the slave server. The master server handles write operations, while the slave server is primarily used for read operations, enhancing read performance and load balancing.
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Data backup and fault recovery: Slave servers can serve as data backups. In the event of a master server failure, the slave can be promoted to a new master rapidly to achieve fault recovery.
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Read-write separation: Read capacity can be expanded by adding more slave servers, whereas write capacity remains constrained to a single master server.
Example scenario: An e-commerce platform where product information is stored in the master database, and numerous user product browsing requests are handled by slave servers, providing fast response times without affecting the master database's performance.
Master-Master Replication
Master-Master Replication is another replication model where two database servers function as both master and slave to each other. This allows each server to handle write operations and synchronize changes to the other server. Key characteristics include:
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Bidirectional synchronous replication: Both servers can accept write operations and synchronize data changes to each other, ensuring data consistency.
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High availability and load distribution: As each server can handle write operations, load can be distributed between the two servers, enhancing system availability and fault tolerance.
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Complex conflict resolution: When both servers may write data, a mechanism is required to resolve data version conflicts.
Example scenario: A global service requiring database servers deployed in different geographical locations. With Master-Master Replication, write requests from users can be processed on geographically closer servers to reduce latency while ensuring data consistency globally.
Summary
Master-Slave Replication is primarily suitable for read-heavy, write-light applications, emphasizing data backup and rapid recovery; whereas Master-Master Replication is suitable for scenarios requiring high availability and low-latency write operations, but it requires more complex conflict resolution mechanisms. Choosing the appropriate replication strategy based on specific business requirements and system architecture is crucial.