Shard

A subset of the data and associated metadata stored in an Eon Mode database. Shards are how Vertica divides the work of processing queries, data loads, and data maintenance between the nodes in a subcluster. Nodes subscribe to one or more shards. When processing a query, each node is responsible for processing the data in the shard or shards to which it subscribes.

The number of shards that data is segmented into depends on the shard count of the namespace to which the data belongs. By default, the database contains a single namespace, default_namespace, with the shard count specified during database setup. You can create additional namespaces using the CREATE NAMESPACE statement.

Shards have a single primary subscriber in the database cluster. The primary subscriber node maintains the data in the shard by running Tuple Mover processes on it.