Creating subclusters

By default, new Eon Mode databases contain a single primary subcluster named default_subcluster.

By default, new Eon Mode databases contain a single primary subcluster named default_subcluster. This subcluster contains all nodes that are part of the database when you create it. You will often want to create subclusters to separate and manage workloads. You have three options to add subclusters to the database:

Create a subcluster using admintools

To create a subcluster, use the admintools db_add_subcluster tool:

$ admintools -t db_add_subcluster --help
Usage: db_add_subcluster [options]

  -h, --help            show this help message and exit
  -d DB, --database=DB  Name of database to be modified
  -s HOSTS, --hosts=HOSTS
                        Comma separated list of hosts to add to the subcluster
                        Database password in single quotes
  -c SCNAME, --subcluster=SCNAME
                        Name of the new subcluster for the new node
  --is-primary          Create primary subcluster
  --is-secondary        Create secondary subcluster
                        Set the number of nodes that will run spread within
                        the subcluster
                        Name of an existing subcluster from which to clone
                        properties for the new subcluster
                        set a timeout (in seconds) to wait for actions to
                        complete ('never') will wait forever (implicitly sets
  -i, --noprompts       do not stop and wait for user input(default false).
                        Setting this implies a timeout of 20 min.

The simplest command adds an empty subcluster. It requires the database name, password, and name for the new subcluster. This example adds a subcluster analytics_cluster to the verticadb database:

$ adminTools -t db_add_subcluster -d verticadb -p 'password' -c analytics_cluster
Creating new subcluster 'analytics_cluster'
Subcluster added to verticadb successfully.

By default, admintools creates the subcluster as a secondary subcluster. You can have it create a primary subcluster instead by supplying the --is-primary argument.

Adding nodes while creating a subcluster

You can also specify one or more hosts for admintools to add to the subcluster as new nodes. These hosts must be part of the cluster but not already part of the database. For example, you can use hosts that you added to the cluster using the MC or admintools, or hosts that remain part of the cluster after you dropped nodes from the database. This example creates a subcluster analytics_cluster and uses the -s option to specify the available hosts in the cluster:

$ adminTools -t db_add_subcluster -c analytics_cluster -d verticadb -p 'password' -s,,

View the subscription status of all nodes in the database with the following query that joins the V_CATALOG.NODES and V_CATALOG.NODE_SUBSCRIPTIONS system tables:

=> SELECT subcluster_name, n.node_name, shard_name, subscription_state FROM
   v_catalog.nodes n LEFT JOIN v_catalog.node_subscriptions ns ON (n.node_name
   = ns.node_name) ORDER BY 1,2,3;

subcluster_name    |      node_name       | shard_name  | subscription_state
analytics_cluster  | v_verticadb_node0004 | replica     | ACTIVE
analytics_cluster  | v_verticadb_node0004 | segment0001 | ACTIVE
analytics_cluster  | v_verticadb_node0004 | segment0003 | ACTIVE
analytics_cluster  | v_verticadb_node0005 | replica     | ACTIVE
analytics_cluster  | v_verticadb_node0005 | segment0001 | ACTIVE
analytics_cluster  | v_verticadb_node0005 | segment0002 | ACTIVE
analytics_cluster  | v_verticadb_node0006 | replica     | ACTIVE
analytics_cluster  | v_verticadb_node0006 | segment0002 | ACTIVE
analytics_cluster  | v_verticadb_node0006 | segment0003 | ACTIVE
default_subcluster | v_verticadb_node0001 | replica     | ACTIVE
default_subcluster | v_verticadb_node0001 | segment0001 | ACTIVE
default_subcluster | v_verticadb_node0001 | segment0003 | ACTIVE
default_subcluster | v_verticadb_node0002 | replica     | ACTIVE
default_subcluster | v_verticadb_node0002 | segment0001 | ACTIVE
default_subcluster | v_verticadb_node0002 | segment0002 | ACTIVE
default_subcluster | v_verticadb_node0003 | replica     | ACTIVE
default_subcluster | v_verticadb_node0003 | segment0002 | ACTIVE
default_subcluster | v_verticadb_node0003 | segment0003 | ACTIVE
(18 rows)

If you do not include hosts when you create the subcluster, you must manually rebalance the shards in the subcluster when you add nodes at a later time. For more information, see Updating Shard Subscriptions After Adding Nodes.

Subclusters and large cluster

Vertica has a feature named large cluster that helps manage broadcast messages as the database cluster grows. It has several impacts on adding new subclusters:

  • If you create a subcluster with 16 or more nodes, Vertica automatically enables the large cluster feature. It sets the number of control nodes to the square root of the number of nodes in the subcluster. See Planning a large cluster.
  • You can set the number of control nodes in a subcluster by using the --control-set-size option in the admintools command line.
  • If the database cluster has 120 control nodes, Vertica returns an error if you try to add a new subcluster. Every subcluster must have at least one control node. The database cannot have more than 120 control nodes. When the database reaches this limit, you must reduce the number of control nodes in other subclusters before you can add a new subcluster. See Changing the number of control nodes and realigning for more information.
  • If you attempt to create a subcluster with a number of control nodes that would exceed the 120 control node limit, Vertica warns you and creates the subcluster with fewer control nodes. It adds as many control nodes as it can to the subcluster, which is 120 minus the current count of control nodes in the cluster. For example, suppose you create a 16-node subcluster in a database cluster that already has 118 control nodes. In this case, Vertica warns you and creates the subcluster with just 2 control nodes rather than the default 4.

See Large cluster for more information about the large cluster feature.