In addition to the shard placement policy, considerations that determine shard placement are:

• Separation of master and replica shards
• Available persistence and Auto Tiering storage
• Rack-zone awareness
• Memory available to host the database when fully populated

The shard placement policies are:

• dense - Place as many shards as possible on the smallest number of nodes to reduce the latency between the proxy and the database shards; Recommended for Redis on RAM databases to optimize memory resources
• sparse - Spread the shards across as many nodes in the cluster as possible to spread the traffic across cluster nodes; Recommended for databases with Auto Tiering enabled to optimize disk resources

When you create a Redis Enterprise Software cluster, the default shard placement policy (dense) is assigned to all databases that you create on the cluster.

You can:

• Change the default shard placement policy for the cluster to sparse so that the cluster applies that policy to all databases that you create
• Change the shard placement policy for each database after the database is created