Frequently Asked Questions
What are Cloud Databases
This is a service of Selectel's cloud platform. Enables rapid cloud deployment of resilient database clusters with PITR recovery.
Setup, configuration, infrastructure maintenance, security and fault tolerance, backups and scaling are performed on the Selectel side.
What is a database cluster
This is one or more database nodes (servers) between which replication is configured.
The primary server of the cluster is the master node. Replicas — exact replicas of the master — can be added to the cluster. If the master becomes unavailable, one of the replicas takes over the master role and a new replica is created in its place (the address of the master node changes). Such a cluster is reliable and is used to support the operation of applications.
How to realize that the cluster has been created and everything is working
A cluster is successfully created and running if the cluster itself and all nodes have the
Can the cluster settings be changed after the cluster has been created
Once the cluster is created, you can modify it:
- cluster name;
- number of replicas in a cluster MySQL, PostgreSQL or Redis;
- cluster server configuration MySQL, PostgreSQL or Redis — depending on the DBMS reduce or increase the number of vCPUs, RAM and disk size;
- the MySQL and PostgreSQL DBMS settings.
You cannot change the subnet to which the cluster is connected.
What can go wrong in cluster operation
In a fault-tolerant cluster, one of the nodes may become unavailable. This means that the node has not sent information that it is in
ACTIVE status for a minute. In this case, we will delete the existing node and replace it with another node.
If a cluster consists only of a master node and it has become unavailable, the cluster also becomes temporarily unavailable — until a new master is created in place of the inactive master. In this case, the databases do not disappear, but become inaccessible for some time. You can contact technical support to resolve the issue or restore the cluster from a backup — MySQL, PostgreSQL or Redis.
What are the limitations
Can be created as part of a single project:
- 10 000 databases within all clusters;
- 1,000 database users.
The number of clusters is limited by the cluster resource quotas — DBaaS vCPU, RAM and local disk. You can increase project limits and quotas.
A cluster can only be created in private and public subnets. A public IP address cannot be used.
How much does it cost to use the Cloud Databases service
Prices for cloud database resources can be viewed at website.
Is it possible to fine-tune the DBMS
The default database settings are picked up and depend on the selected cluster node configuration.
What happens if the cluster node disk runs out of space
If the cluster disk is 80% full, a notification will automatically be sent to the account's email.
If the cluster disk is 95% or more full, the cluster will go to
DISK_FULL status and will be read-only. To keep the cluster running on read and write, clean up the disk or scale the cluster MySQL, PostgreSQL or Redis and select a configuration with a larger disk size.