Enabling large cluster
Vertica enables the large cluster feature automatically when:
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The total number of nodes in the database cluster exceeds 120.
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You create an Eon Mode subcluster with more than 16 nodes.
In most cases, you should consider manually enabling large cluster before your cluster size reaches either of these thresholds. See Planning a large cluster for guidance on when to enable large cluster.
You can enable large cluster on a new Vertica database, or on an existing database.
Enable large cluster when installing Vertica
You can enable large cluster when installing Vertica onto a new database cluster. This option is useful if you know from the beginning that your database will benefit from large cluster.
The install_vertica script's
--large-cluster argument enables large cluster during installation. It takes a single integer value between 1 and 120 that specifies the number of control nodes to create in the new database cluster. Alternatively, this option can take the literal argument default. In this case, Vertica enables large cluster mode and sets the number of control nodes to the square root of the number nodes you provide in the
--hosts argument. For example, if --hosts specifies 25 hosts and --large-cluster is set to default, the install script creates a database cluster with 5 control nodes.
The --large-cluster argument has a slightly different effect depending on the database mode you choose when creating your database:
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Enterprise Mode:
--large-clustersets the total number of control nodes for the entire database cluster. -
Eon Mode :
--large-clustersets the number of control nodes in the initial default subcluster. This setting has no effect on subclusters that you create later.
Note
You cannot use --large-cluster to set the number of control nodes in your initial database to be higher than the number of you pass in the --hosts argument. The installer sets the number of control nodes to whichever is the lower value: the value you pass to the --large-cluster option or the number of hosts in the --hosts option.
You can set the number of control nodes to be higher than the number of nodes currently in an existing database, with the meta-function SET_CONTROL_SET_SIZE function. You choose to set a higher number to preallocate control nodes when planning for future expansion. For details, see Changing the number of control nodes and realigning.
After the installation process completes, use the Administration tools or the Management Console to create a database. See Create an empty database for details.
If your database is on-premises and running in Enterprise Mode, you usually want to define fault groups that reflect the physical layout of your hosts. They let you define which hosts are in the same server racks, and are dependent on the same infrastructure (such power supplies and network switches). With this knowledge, Vertica can realign the control nodes to make your database better able to cope with hardware failures. See Fault groups for more information.
After creating a database, any nodes that you add are, by default, dependent nodes. You can change the number of control nodes in the database with the meta-function SET_CONTROL_SET_SIZE.
Enable large cluster in an existing database
You can manually enable large cluster in an existing database. You usually choose to enable large cluster manually before your database reaches the point where Vertica automatically enables it. See When To Enable Large Cluster for an explanation of when you should consider enabling large cluster.
Use the meta-function SET_CONTROL_SET_SIZE to enable large cluster and set the number of control nodes. You pass this function an integer value that sets the number of control nodes in the entire Enterprise Mode cluster, or in an Eon Mode subcluster.