With Data Management for VMware Tanzu, you can configure High Availability (HA) clusters of MySQL databases or PostgreSQL databases. As a Provider Administrator, Organization Administrator, or Organization User, you can create Replica databases of a Primary Database to support redundancy. One or more Replica databases and a Primary database can form an HA cluster of MySQL databases. However, to form an HA cluster of PostgreSQL databases, you need one or more Replica databases and a Primary database along with a Monitor database.

If the Primary Database in an HA cluster stops its services, there is automatic promotion of one of the configured Replica databases as the Primary database. To support changing resource requirements of a business, you can promote a Replica database to a Primary database manually.

Limitations for Configuring High availability Clusters

The following limitations are applicable when configuring an HA cluster of databases:

  • You cannot configure an HA cluster on Microsoft SQL Server databases.
  • You can configure a maximum of five nodes in an HA cluster that can include a Primary database, Replica databases, and a Monitor database.
  • If you don't configure the maintenance policy of an HA cluster considering the number of nodes, automatic updates for all the nodes is not simultaneous during the maintenance window. You can configure approximately 15 minutes to 20 minutes of maintenance time per node. For example, if an HA cluster has five nodes, you can configure the Duration of the maintenance policy of the Primary database as 100 minutes or more. For more information, see Updating Database Maintenance Policy.
  • You cannot create an HA cluster from the databases upgraded from releases earlier than 1.3.0. If you want to create a cluster from the upgraded databases, you must clone or restore the database, and then create an HA cluster using the cloned or restored database as the Primary database of the cluster.
  • You can manually promote a Replica database to a Primary database only if its status is Online.
  • For promotion of a MySQL replica database, status of all the databases in the cluster must be Online. So, if any database in the cluster is powered off, you must power it on (if possible) or remove it from the cluster.
  • If the PostgreSQL Monitor database is down, the HA cluster is not functional (auto promotion does not work), but operations like backup, cloning, and restore can be performed on the databases of the HA cluster.
  • When you configure the first Replica database of a MySQL HA cluster, you must specify the Cluster IP as a static and valid IP address that is in the subnet of the Primary databases's application network. You cannot provide the Cluster IP for the subsequent Replica databases that you create for that cluster.

Creating High Availability Clusters

You can create HA clusters of MySQL databases or PostgreSQL databases in a sync mode to support immediate sync between the Primary database and Replica databases in an HA cluster. In an HA cluster of PostgreSQL databases, a PostgreSQL Monitor database is created automatically when you create the first Replica database of the cluster.

Perform the following steps to create an HA cluster of MySQL databases or PostgreSQL databases:

  1. Click a database from the list of databases in the Databases view of the Databases pane.

    The Details tab of the database appears.

  2. Click the Cluster Settings tab and then click + CREATE in the Replication section of this tab.

  3. In the Create Read Replica form, specify the following properties, and then click CREATE.

    Property Description
    Replica VM Name Enter the Replica VM name for the Replica database.
    Namespace Select the Namespace for the Replica database.
    Cluster IP Enter a static valid IP address that is in the subnet of the Primary databases's application network. You cannot provide the Cluster IP for the subsequent Replica databases you create for that cluster. This property is not available for PostgreSQL replica database VMs.
    Candidate Priority Specify a value between 0 to 100. Higher the Candidate Priority, greater the chance of the Replica database to be auto promoted as the Primary database.

A Read Replica database is created for a MySQL HA cluster and a Monitor database is created along with the first Read Replica database for a PostgreSQL HA cluster.

HA Status of High Availability Clusters

Create at least two replicas in an HA cluster for efficient functioning of automatic promotion in the cluster. Based on the number of Replica databases created in an HA cluster, the status of the cluster varies as follows:

  • The status is Unconfigured for HA clusters that have no Replica database.
  • The status is Incomplete for HA clusters that have at least one Replica database with Replication Status as Active.
  • The status is Complete for HA clusters that have more than one Replica database with Replication Status as Active.

Manual Promotion in High Availability Clusters

You can use Data Management for VMware Tanzu to manually promote a Replica database that is in Online status to a Primary database.

div class="note">Note: To perform manual promotion in a High availability cluster of databases, all the database VMs in the cluster must have Online status. If any database VM in a cluster is powered off, either power it on or remove it from the cluster before you attempt manual promotion in the cluster.

Perform the following steps to manually promote a Replica database to a Primary database:

  1. Click the Replica database in the Databases view of the Databases pane.

    The Details tab of the Replica database appears.

  2. Click the Cluster Settings tab.

  3. In the Replication section of the Cluster Settings tab, click the three vertical dots in Actions column of the Replica database, and then select Promote Replica from the pop-up menu.

  4. In the Promote Read Replica dialog box, click CONFIRM.

The Replica database is promoted as the Primary database, and the existing Primary database becomes a Replica database.

Deleting Databases in High availability Clusters

Data Management for VMware Tanzu enables you to delete databases in an HA cluster. For a MySQL HA cluster, you must delete the Replica databases before you delete the Primary database of the cluster. For a PostgreSQL HA cluster, you must delete the Replica databases, followed by the Primary database, and then the Monitor database of the cluster.

Perform the following steps to delete a database in an HA cluster:

  1. Click the Replica database or Primary database in the Databases view of the Databases pane.

    The Details tab of the Replica database or Primary database appears.

  2. Click the Cluster Settings tab.

  3. In the Replication section of the Cluster Settings tab, click the three vertical dots in Actions column of the Replica database, and then select Delete from the pop-up menu.

  4. In the Delete Instance dialog box, click CONFIRM.

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