Questions about ClickHouse
Why should I use ClickHouse in Managed Service for ClickHouse and not my own installation on a VM?
Managed Service for ClickHouse automates routine database maintenance:
- Quick DB deployment with the necessary available resources.
- Data backup.
- Regular software updates.
- DB cluster failover.
- Database usage monitoring and statistics.
When should I use ClickHouse instead of PostgreSQL?
ClickHouse supports only adding and reading data, as it is designed primarily for analytics (OLAP). In other cases, it is probably more convenient to use PostgreSQL.
Is it possible to connect to individual ClickHouse hosts?
Yes, you can. You can connect to the hosts of a ClickHouse cluster via an encrypted connection:
SSH connections are not supported.
How can I load data to ClickHouse?
Use the INSERT query described in the documentation on ClickHouse.
How do I load a very large amount of data to ClickHouse?
Use the CLI for efficient data compression during transmission (the recommended frequency is no more than one INSERT command per second).
Data transfer from physical media is not yet supported.
What happens to a cluster if one of its nodes fails?
DB clusters consist of at least two replicas, so the cluster will continue working if one of its nodes is out.
Data may be lost only if a node with a non-replicated table fails.
Is it possible to deploy a ClickHouse DB cluster in multiple availability zones?
Yes, you can. A database cluster may consist of hosts that reside in different availability zones and even different availability regions.
How can I back up a ClickHouse database?
Backups are created every 24 hours and stored for seven days after being created. You can restore data only as of backup creation time.
How does replication work for ClickHouse?
ZooKeeper is used for replication. Managed Service for ClickHouse creates a separate ZooKeeper cluster for each ClickHouse cluster.
Access to ZooKeeper and its setup are not available to Cloud users.
Why does a ClickHouse cluster take up 3 hosts more than it should?
When creating a ClickHouse cluster with two or more hosts, Managed Service for ClickHouse automatically creates a cluster of three ZooKeeper hosts for managing replication and fault tolerance. These hosts are considered when calculating the resource quotas used in the cloud and when calculating the cost of the cluster. By default, ZooKeeper hosts are created with a minimal host class.
For more information about using ZooKeeper, see ClickHouse documentation.