Installation - consensys/quorum

Quorum is a consensus algorithm used by various Hashicorp products, including Consul and Vault, to ensure high availability and fault tolerance. In this guide, we will focus on deploying and installing Quorum for Hashicorp’s Vault and Consul.

Understanding Quorum

Quorum is a consensus algorithm that requires a majority of members from a peer set to be available for the system to function. The number of members required for a quorum depends on the size of the peer set. For instance, in a peer set of size n, a quorum requires at least (n/2)+1 members.

Quorum is crucial for maintaining the availability and consistency of distributed systems. In the event of a failure, if a quorum of nodes is unavailable, the system becomes unavailable, and no new logs can be committed.

Vault and Quorum

Vault, a secrets management system by Hashicorp, uses Quorum to ensure high availability and fault tolerance. Vault’s Integrated Storage, which is the default storage backend, is eventually consistent. This means that only the leader node can write to the Vault storage and replicate the change to the follower nodes.

To ensure a minimum failure tolerance, the Vault Reference Architecture recommends a 5-node cluster. This setup guarantees a minimum failure tolerance of at least 2 nodes. In the event of maintenance or other changes, additional nodes can be added to the cluster, ensuring a higher failure tolerance.

Consul and Quorum

Consul, a distributed service discovery and configuration management tool by Hashicorp, also uses Quorum to ensure high availability and fault tolerance. Consul’s server Quorum Size and Failure Tolerance can be configured according to the number of servers in the cluster.

Best Practices for Deploying Quorum

Hashicorp provides several best practices for deploying Quorum:

Deploying an odd number of servers in the peer set is recommended to ensure a quorum can always be formed.
For most deployments, it is recommended to deploy three to five servers for both Vault and Consul deployments.
In large deployments, non-voting or read replication features can be used to scale reads without impacting write latency.

Quorum Fixer

Quorum Fixer is a tool built by Meta in anticipation of unexpected quorum failures. It helps mitigate situations where automation fails to detect unhealthy instances and replace them quickly.

Conclusion

In this guide, we have explored the concept of Quorum, its importance in Hashicorp’s Vault and Consul, and best practices for deploying and installing Quorum. By following these guidelines, you can ensure the high availability and fault tolerance of your Vault and Consul deployments.

For more detailed information, please refer to the following resources: