Question - Consul multi datacenter deployment

[guillaumeldc]

Thanks for the library, this has been very helpful so far. I'm trying different failure scenarios and there are a few things I have trouble understanding.

I'm using Consul with nodes deployed in 2 datacenter. DC1: 3 servers, 1 client DC2: 3 servers, 1 client

My understanding is that the raft protocol and Consul should work with 2 wan federated cluster in these two datacenter.

The setup with patroni however seems to require the use of only one cluster across 2 different datacenter. My questions are as follows:

• I would need to remove or add one node to bring the total of nodes to either 5 or 7 (DC1: 2 or 3, DC2: 3 or 4) and adjust to quorum to either 3 or 4. Correct?
• I understand, the fault tolerance would either be 3 or 2 nodes but what if I lose DC2 (the one with most nodes) completely?

thank you in advance for your help.

[vitabaks]

Hi @guillaumeldc,

To ensure quorum, (N/2) + 1 nodes are required. You can find more details about how Raft works here. When distributing the DCS across multiple data centers, a third data center is necessary. More information on this can be found here.

If the second data center is only intended for Disaster Recovery (DR), you can set up two independent DCS clusters: one for the main Patroni cluster and another for the Standby Cluster (variable patroni_standby_cluster).