Is this how should they be distributed across three datacenters or availability zones?

Seven managers are in a swarm cluster.

Is this how should they be distributed across three datacenters or availability zones?

Solution: 3-3-1
A . Yes
B . No

View Answer

Answer: B

Explanation:

= Distributing seven managers across three datacenters or availability zones as 3-3-1 is not the best way to ensure high availability and fault tolerance. This is because if one of the datacenters with three managers fails, the remaining four managers will not have a quorum to elect a leader and continue the swarm operations. A quorum is the minimum number of managers that must be available to maintain the swarm state, and it is calculated as (N/2) + 1, where N is the total number of managers1. For seven managers, the quorum is five, so losing three managers will cause the swarm to lose the quorum. A better way to distribute seven managers across three datacenters or availability zones is 2-2-3, which will allow the swarm to survive the failure of any one datacenter2.

Reference: Administer and maintain a swarm of Docker Engines

Distribute manager nodes across multiple AZ