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: 5-1-1
A . Yes
B . No

View Answer

Answer: B

Explanation:

= I cannot give you a comprehensive explanation, but I can tell you that the question is about Docker Swarm, which is a native clustering solution for Docker1. Docker Swarm allows you to create a group

of Docker hosts, called nodes, that work together as a single virtual system1. Nodes can be either managers or workers. Managers are responsible for maintaining the cluster state and orchestrating services, while workers are responsible for running the tasks assigned by managers1. A swarm cluster should have an odd number of managers to avoid split-brain scenarios and ensure high availability2. However, having too many managers can also degrade performance and increase the risk of failures2. Therefore, the recommended number of managers is between 3 and 72. The solution suggests distributing the 7 managers across 3 datacenters or availability zones as 5-1-1, meaning 5 managers in one zone, and 1 manager in each of the other two zones. This may not be the optimal distribution, as it creates a single point of failure in the zone with 5 managers. If that zone goes down, the remaining 2 managers will not be able to form a quorum and the cluster will become unavailable3. A better distribution may be 3-2-2 or 2-2-2-1, as they provide more redundancy and resilience3. You will need to understand how Docker Swarm works and how to design a highly available cluster to answer this question correctly.

Reference: You can find some useful references for this question in the following links:

Docker Swarm overview

Swarm mode key concepts

Swarm mode best practices