What Is Managed Databases?
Managed Databases is a service that makes it possible to deploy database clusters in the cloud.
All administration tasks, such as setting up, configuration, maintenance, and security will be handled by Selectel. Managed Databases is one of the services of the Selectel Cloud Platform. This service can be used by all clients who have added funds to the balance.
What Is a Database Cluster?
Database Cluster is one or a combination of several database servers with replication set between them.
Cluster servers have different roles. The main server in the cluster is called the master. You can add replicas to the cluster (replicas are the exact copies of the master). If the master becomes unavailable, then one of the replicas takes over the role of the master, and a new replica is created instead (in this case, the address of the master changes). This cluster is reliable and is used for apps support.
How Can I Understand That the Cluster Is Created?
If the cluster is created successfully, it has the Active status.
Can I Change the Cluster Settings after It Is Created?
You can change the following settings after the cluster is created:
- Cluster name;
- The number of replicas in the cluster — you can increase the number of replicas only if there are free addresses in the subnet that the cluster is connected to;
- Cluster server configuration — you can choose the configuration with a larger disk size.
After creating a cluster, you cannot change the Subnet that the cluster is connected to.
What Can Go Wrong With the Cluster?
One of the cluster servers may become unavailable. This means that the server did not send information about its Active status for a minute. In this case, we delete the existing machine and replace it with another one.
If the cluster consists only of the master and the master becomes unavailable, the cluster temporarily becomes unavailable until a new one is created instead of the inactive master. In this case, the user’s databases also become unavailable for some time (but they are not deleted).
Are There Any Limits?
User can create:
- 50 databases in one cluster;
- 50 users in one cluster.
The number of database clusters is limited by quotas for cluster resources – DBaaS vCPU, RAM, and local disk.
You can create a cluster only on private and public subnets. You cannot use the public IP.
What Are the Costs for the Managed Databases Service?
The costs for the database resources are provided on our website.
Which DBMS Will Be Available In the Service?
We are planning to add Redis, MongoDB, Microsoft SQL.
Is It Possible to Fine-Tune the DBMS in the Managed Databases service?
The database settings are selected by default and depend on the selected server configuration. We are planning to implement the possibility of self-tuning the DBMS in the future.
What Happens If the Cluster Disk Runs out of Space?
The cluster will automatically switch to read-only mode. In this case, the cluster status will switch to DISK_FULL, and several tickets will be sent to the account owner that the write mode is unavailable because the disk is full. You need to select a configuration with a larger disk size to resume the cluster.