Shard (database architecture)
（重定向自Sharding）
A database shard is a horizontal partition of data in a database or search engine. Each individual partition is referred to as a shard or database shard. Each shard is held on a separate database server instance, to spread load.
Some data within a database remains present in all shards, but some only appears in a single shard. Each shard (or server) acts as the single source for this subset of data.