Comparison
Cattle not petsvsImmutable infrastructure
Cattle not pets
nobody knows the names of the machines, and the fix for a sick one is to terminate it rather than to log in.
The doctrine that infrastructure should be numerous, identical and disposable rather than individually named and nursed. It is a statement about operational posture rather than technology: the test is whether replacing any given machine is a routine, automated non-event. Where it fails is where it always fails — the one host with something on its local disk that nobody has written down.
Full entry →Immutable infrastructure
you never patch a running server; you build a new image and replace the instance entirely.
Treating deployed artefacts as read-only and replacing rather than modifying them. It eliminates configuration drift and makes environments reproducible from source. It requires the build and replace cycle to be fast, and it makes stateful nodes the special case that needs a real plan.
Full entry →