7.3

You can configure the database as a single node or with multiple nodes to facilitate high availability
through failover. The vRealize Automation installer includes a database node on each vRealize
Automation appliance installation. So if you install three instances of a vRealize Automation appliance,
you have three database nodes. Automatic failover is implemented on applicable deployments. The
appliance database requires no maintenance unless a machine configuration changes or, if you use a
clustered configuration, you promote a different node for the master.
Note The database clustered configuration is set up automatically when you join a virtual appliance to
the cluster using the Join cluster operation. The database cluster is not directly dependent upon the
virtual appliance cluster. For instance, a virtual machine joined to a cluster can operate normally even if
the embedded appliance database is not started or has failed.
For high availability, vRealize Automation uses the PostgresSQL master-replica model to support data
replication. This means that all of the database nodes work in a cluster with one leading node, known as
the master, and several replicating nodes, known as replicas. The master node handles all database
requests and the replica nodes stream and replay transactions from the master locally.
A clustered configuration contains one master node and one or more replica nodes. The master node is
the vRealize Automation appliance node with the master database that supports system functionality.
Replica nodes contain copies of the database that can be pulled into service if the master node fails.
Several high availability appliance database options exist. Selecting the replication mode is the most
important database configuration option. The replication mode determines how your vRealize Automation
deployment maintains data integrity and, for high availability configurations, how it fails over if the master
or primary node fail. There are two available replication modes: synchronous and asynchronous.
Both replication modes support database failover, though each has advantages and disadvantages. To
support high availability database failover, asynchronous mode requires two nodes, whereas
synchronous mode requires three nodes. Synchronous mode also invokes automatic failover.
Replication Mode Advantages Disadvantages
Synchronous
n
Minimizes chance of data loss.
n
Invokes automatic faiiover.
n
Might affect system performance.
n
Requires three nodes.
Asynchronous
n
Requires only two nodes.
n
Affects system performance less
than synchronous mode.
Not as robust as synchronous mode in
preventing data loss.
vRealize Automation supports both modes, but operates in asynchronous mode by default and provides
high availability only if there are at least two appliance database nodes. The Database tab on the Virtual
Appliance Management Interface enables you to switch synchronization modes and to add database
nodes as needed.
When operating in synchronous mode, vRealize Automation invokes automatic failover.
If you begin with one node in a non-high-availability configuration, you can add nodes later as required to
enhance high availability. If you have the appropriate hardware and require maximum protection against
data loss, consider configuring your deployment to operate in synchronous mode.
Managing vRealize Automation
VMware, Inc. 30