Relationship between service resources
The main entity used in Managed Service for ClickHouse is a database cluster.
Each cluster consists of one or more database hosts, which are virtual machines with DBMS servers deployed on them. Cluster hosts may reside in different availability zones and even different availability regions. Learn more about Yandex.Cloud geography.
A cluster consisting of multiple hosts has automatic failover, because the hosts can take over each other's functions as the cluster's primary replica.
A single-host cluster doesn't guarantee fault tolerance. To add replicas, first add the ZooKeeper hosts that manage replication and query distribution across the cluster hosts.
When creating a cluster, specify:
Host class: A VM template for deploying the cluster hosts. For a list of available host classes and their characteristics, see Host classes.
Environment: The environment where the cluster will be deployed:
PRODUCTION: For stable versions of your apps.
PRESTABLE: For testing, including the Managed Service for ClickHouse service itself. The Prestable environment is first updated with new features, improvements, and bug fixes. However, not every update ensures backward compatibility.
You should also specify the host class when creating a shard.
A database cluster created in a folder can be accessed by all VMs connected to the same cloud network. Learn more about networking.
The service can automatically access the system and diagnostic information of your databases to plot monitoring graphs and maintain the health of your cluster. The service never queries or uses the data that you saved to the database.