Relationship between service resources
Redis is a high-performance key-value store that runs in RAM. Managed Service for Redis lets you easily create Redis host clusters with a high level of fault tolerance.
The main entity used in Managed Service for Redis 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 3 and more hosts has automatic failover, because the hosts can take over each other's functions as the cluster's primary replica.
A cluster of one or two hosts is cheaper, but it doesn't guarantee fault tolerance.
When creating a cluster, you need to specify the host class, which is a VM template for deploying the cluster hosts. For a list of available host classes and their characteristics, see Host configurations.
The amount of memory allocated to a host is also determined by the
maxmemory configuration parameter for Redis hosts: the max amount of data is 75% of the available memory. For example, for a host class with 8 GB RAM, the
maxmemory value will be 6 GB.
A DB cluster connected to a cloud network can be accessed by all VMs connected to the same cloud network. Learn more about networking.
The service may automatically request system and diagnostic data about your databases to draw monitoring graphs and maintain the operability of the cluster. The service never requests or uses the data you inserted into databases yourself.