https://joachim8675309.medium.com/devops-concepts-pets-vs-cattle-2380b5aab313

This is one of the cardinal concepts in DevOps is the notion of pets vs cattle for the service model. This was first introduced by Bill Baker on topic of scaling up vs scaling out presentation that was included slide deck titled Scaling SQL Server 2012. It was later introduced popularized by Gavin McCance in CERN Data Centre Evolution presentation.

Pets Service Model

In the pets service model, each pet server is given a loving names like zeus, ares, hades, poseidon, and athena. They are “unique, lovingly hand-raised, and cared for, and when they get sick, you nurse them back to health”. You scale these up by making them bigger, and when they are unavailable, everyone notices.

Examples of pet servers include mainframes, solitary servers, load balancers and firewalls, database systems, and so on.

Cattle Service Model

In the cattle service model, the servers are given identification numbers like web01, web02, web03, web04, and web05, much the same way cattle are given numbers tagged to their ear. Each server is “almost identical to each other” and “when one gets sick, you replace it with another one”. You scale these by creating more of them, and when one is unavailable, no one notices.

Examples of cattle servers include web server arrays, no-sql clusters, queuing cluster, search cluster, caching reverse proxy cluster, multi-master datastores like Cassandra, big-data cluster solutions, and so on.