Resource relationships in Managed Service for PostgreSQL
The main entity used in Managed Service for PostgreSQL is a database cluster.
Each cluster consists of one or more DB hosts, which are virtual machines with DBMS servers deployed. Cluster hosts may reside in different availability zones. You can learn more about Yandex Cloud availability zones in Platform overview.
A cluster of two or more hosts is natively highly available because one of its replica hosts will assume the master role upon the current master host's failure. To learn more about how the number of hosts affects cluster availability, see the relevant section.
Note
A replica that has an explicitly specified replication thread source cannot take the master role. To learn more, see Replication.
The minimum number of hosts in a cluster depends on the selected disk type. The default cluster configuration offered in the management console includes two hosts.
Warning
We do not recommend creating a cluster having a single host. While being cheaper, such a cluster is anything but highly available.
A cluster's computing capacity depends on its host class, which is the virtual machine template used to deploy the cluster's hosts. For a list of available host classes and their specs, see Host classes.
To manage connections and balance the cluster load, the service architecture features the Odyssey connection pooler. For more information, see Managing connections.
A cluster created in a folder can be accessed by all VMs connected to the same cloud network. For more information about networking, see the Virtual Private Cloud documentation.
Alert
The service can automatically access the system and diagnostic information of your databases to build monitoring charts and maintain your cluster health. The service never queries or uses the data you saved to the database.
Be mindful of what is what is controlled by the service, and what by the Yandex Cloud customer. Understanding these control zones will help you use your cloud resources effectively and avoid potential database-related problems. For more information, see Zones of control between managed database (MDB) service users and Yandex Cloud.