Mongodb sharding Terminology

sharding refers to data fragmentation

cluster cluster, a cluster contains multiple shards, each shard consists of a replica set

Collection The concept of a table in db, except that there is no schema

Each collection in the sharding scene is divided into multiple chunks,chunk size can be set

Chunk if it exceeds the set size, it will be split into two,splitting is responsible for the work of the background process.

migrate refers to the chunk migration, when the Shard between different chunk the number of uneven, background process balancing will perform migrate work.

A cluster of more than three servers is responsible for recording which chunk is located on which Shard, which records metadata, metadata. These servers are called config server

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Mongodb sharding Terminology