MySQL Group Replication is a plugin that enables synchronous replication in a group of MySQL servers, providing fault-tolerant, highly available distributed storage with automatic synchronization. It is based on a new replication protocol with a group membership service, which ensures that all servers have an up-to-date copy of the data. This technology was introduced in MySQL 5.7.17 and is a built-in component in the MySQL Community edition.
Group Replication has several advantages over traditional master-slave replication in terms of consistency and fault tolerance. First, it provides a more consistent view of the database across all nodes. In traditional master-slave replication, there is typically one master server that handles all writes and updates to the database, and multiple slave servers that receive copies of the data. This can result in delays or inconsistencies in replication, leading to potentially different data sets on different nodes.
In Group Replication, all nodes are equal peers and have the same level of authority to accept updates. This makes it possible for clients to write or read to any node in the group, and any updates will be propagated to all other nodes in real-time, making sure the data is always consistent across all nodes.
Second, Group Replication provides fault tolerance by allowing the group to continue functioning even if some nodes fail or are temporarily unavailable. In traditional master-slave replication, if the master fails, the entire system becomes unavailable until the master is replaced. In Group Replication, if a node fails, a new node can be added to the group to replace it, and data will continue to be available without interruption.
Group Replication uses a Multi-Master topology, where all nodes in the group act as masters and receive updates from other nodes in real-time. This means that any node can accept updates, and those updates are automatically propagated to other nodes in the group. The fault-tolerant nature of the group is achieved through group membership management, where each node is aware of the status of other nodes in the group.
In conclusion, MySQL Group Replication provides a more consistent and fault-tolerant replication method compared to traditional master-slave replication. It ensures that all nodes have an up-to-date copy of the data and can accept updates independently, making it much more resilient to failures of single nodes.