Managed Databases service allows you to increase or decrease the number of replicas in the cluster, as well as change the server configuration to provide better performance of the database cluster.
Changing the Configuration of Servers in a Cluster
You can only change the configuration of the database servers upwards due to the limits on the disk space.
Follow these steps to change the configuration of the cluster servers:
- Go to the Settings section on the cluster page.
- Click Scale cluster and select the required configuration.
- Save your changes. The cluster’s status will change to RESIZING. The time that the cluster will remain in this status depends on the amount of data in the cluster.
- After successfully applying the changes, the cluster’s status will change to ACTIVE.
The configuration change process is different for clusters with and without replicas.
If there are no replicas in the cluster, the master will be stopped to apply the changes. Because of this, the cluster will be temporarily unavailable for read and write operations. After applying the changes, the master will start and the cluster will be available again.
If the cluster has replicas, scaling will not affect its operation — the cluster will be available for read and write operations as the changes are applied. For a cluster with replicas, the configuration change will look as follows:
- first, the replicas are stopped one by one, and the configuration of each of them is changed;
- after all replicas are scaled, the master switches to one of the replicas;
- the «former master» is scaled.
Changing the Number of Replicas
The presence of replicas in a cluster affects its fault tolerance. We recommend creating fault tolerant clusters consisting of the master and replicas.
Follow these steps to change the number of replicas in a cluster:
- Click Scale cluster on the cluster settings page.
- Select the required number of replicas. Please note that each new replica takes a new address in the subnet. You cannot add replicas to the cluster if there are no free addresses on the subnet that the cluster is connected to.
- Save your changes.
The cluster’s status will change to RESIZING. The cluster still will be available in this status.
After the operation is completed, the cluster’s status will change to ACTIVE.