Shards and Subscriptions

In Eon Mode, the primary data storage is shared withVertica database nodes. Vertica segments (partitions) the data into shards. Each node in your database subscribes to a subset of the shards in the communal storage location. This ensures that if a node goes down or a node is being used in another query, all the data is available on the remaining nodes. When K-Safety is 1 or higher (high availability), each shard has more than one node subscriber.

The shards in your communal storage location are similar to a collection of segmented projections in an Enterprise Mode database. You define the number of shards at the time you create your database.

For efficiency, Vertica transfers metadata about shards directly between database nodes. This peer-to-peer transfer applies only to metadata; the actual data that is stored on each node gets copied from communal storage to the node's depot as needed.

Expanding Your Cluster

This diagram shows the process of expanding a 3-node 3-shard database to 6 nodes. The number of shards stays the same and the additional nodes gain subscriptions to the shards. When nodes join the cluster they immediately subscribe to shards and begin the process of populating their depots.