Cluster
Each DDS cluster consists of a config node, and multiple mongos and shard nodes. The following diagram shows the node relationships.
Figure 1 Diagram of node relationships
mongos
A mongos is a router for reading and writing data, providing a unified interface for accessing DB instances.
- Each DB instance has 2 to 32 mongos. You can specify the quantity.
- A mongos reads configuration settings from configs and allocates read and write requests to shards. You can connect to a mongos directly.
config
A config stores configuration settings for DB instances and consists of one replica set.
- A high availability config is required for deploying a DB instance or modifying the instance information.
- You cannot connect to a config directly.
shard
Shards are used to store user data.
- Each DB instance of Community Edition has 2 to 32 shards. You can specify the quantity.
- Each shard is deployed as a replica set to ensure data redundancy and high reliability.
- You cannot connect to a shard directly.
Parent topic: Basic Concepts
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