Use the cassandra command of the cell management tool to connect the cell to an optional metrics database.

VMware Cloud Director can collect metrics that provide current and historic information about virtual machine performance and resource consumption. Use this subcommand to configure an Apache Cassandra database for use as a VMware Cloud Director metrics repository. Use the cell-management-tool configure-metrics subcommand to tool to configure the set of metrics to collect. See Configure Metrics Collection and Publishing in VMware Cloud Director.

Data for historic metrics is stored in an Apache Cassandra database. See Install and Configure a Cassandra Database for Storing Historic Metric Data for more information about configuring optional database software to store and retrieve performance metrics.

To create a connection between VMware Cloud Director and an Apache Cassandra database, use a command line with the following form: 
cell-management-tool cassandra options
Table 1. Cell Management Tool Options and Arguments, cassandra Subcommand
Command Argument Description
--help (-h) None Provides a summary of available options for this command.
--add-rollup None Updates the metrics schema to include rolled-up metrics. See Install and Configure a Cassandra Database for Storing Historic Metric Data.
--cluster-nodes address [, address ... ] Comma-separated list of Cassandra cluster nodes to use for VMware Cloud Director metrics.
--clean None Remove Cassandra configuration settings from the VMware Cloud Director database.
--configure None Configure VMware Cloud Director for use with an existing Cassandra cluster.
--dump None Dump the current connection configuration.
--keyspace string Set VMware Cloud Director key space name in Cassandra to string. Defaults to vcloud_metrics.
--offline None Cofigure Cassandra for use by VMware Cloud Director, but do not test the configuration by connection to VMware Cloud Director.
--password string Password of Cassandra database user
--port integer Port to connect to at each cluster node. Defaults to 9042.
--ttl integer Retain metrics data for integer days. Set integer to 0 to retain metrics data forever.
--update-schema None Initializes the Cassandra schema to hold VMware Cloud Director metrics data.
--username string User name of the Cassandra database user.

Configuring a Cassandra Database Connection

Use a command like this, where node1-ip, node2-ip, node3-ip, and node4-ip are the IP address of the members of the Cassandra cluster. The default port (9042) is used. Metrics data is retained for 15 days. 

[root@cell1 /opt/vmware/vcloud-director/bin]# ./cell-management-tool cassandra --configure --create-schema \
--cluster-nodes node1-ip,node2-ip,node3-ip, node4-ip \
--username admin --password 'P@55w0rd' --ttl 15

You must restart the cell after this command completes.