Buenas tardes:
I am reviewing the DR topic, but I have some doubts about the concept, I appreciate if someone supports me with any of these questions:
Is the DR configured as passive?
What is the general function of DR, this machine replicates the database (users, credentials and configurations) or what is the information that it synchronizes?
How is the use of this DR machine justified for a client, so that this license is considered?
What are the advantages of having HA (1 master + 2 Slave) against HA (1 master + 1 Slave) + DR?
1 - It will depend on the environment and disaster recovery plan. So if you have a server of senhasegura to use as a Disaster Recovery, you can set it up as passive.
Disasters Recovery is considered to be a plan to execute as an action to recover your system. And can be a server as passive, a backup pan in a remote partition of the server and a different data center, or a third server on the senhasegura cluster in another data center.
2 - The DR machine must be in the cluster of senhasegura nodes, so there will be a replication of the data (user, credentials, videos, etc.)
3 - The idea of having a server for DR is not to have just a single point to failure. For example, have two servers in a data center, and have a third in a different one. If the first data center goes down, the customer has a third server intact to restore the system.
4 - Both HA scenarios are a cluster of 3 nodes. The only difference between them is a cluster of 3 active nodes. It will be possible to access and use all the three load balancers between the three nodes.
On the environment of the two actives + DR, the access will happen only on the two server actives, and the DR will replicate.