Docker Swarm vs Kubernetes

Docker Swarm is an open-source, free orchestration mode built into Docker Engine for managing clusters of Docker daemons in production. It is controlled through the Docker CLI and needs no separate orchestration software. Managers maintain a declarative desired state covering replica counts, networks, storage resources, and exposed ports. Services can be replicated across selected nodes or run globally with one task on every node. Overlay networks connect daemons, while an ingress network provides load balancing. Swarm assigns DNS names and supports virtual-IP load balancing or DNS round-robin discovery. Updates can roll out incrementally and roll back to an earlier service version. Nodes authenticate and encrypt communications with mutual TLS, requiring at least TLS 1.2. Overlay application traffic is not encrypted by default; IPsec encryption can reduce performance. Swarm is self-hosted, supports rolling updates and policy controls, and lacks multi-cluster management and autoscaling.

Kubernetes is an open-source system for automating deployment, scaling, and management of containerized applications. It supports stateless, stateful, and data-processing workloads, and can run locally, in a cloud, or in a datacenter; users can also choose a managed service rather than operate a cluster themselves. It coordinates gradual updates while monitoring application health and can roll back a change if something goes wrong. Pods receive IP addresses and groups of Pods can share a DNS name, with load balancing across them. Kubernetes can mount storage from local, public-cloud, or network systems such as iSCSI or NFS. Secrets and configuration can be updated without rebuilding images. Scaling can be manual or automatic based on CPU use. Security mechanisms include Secrets, Pod security standards, RuntimeClasses, network policies, admission controllers, and audit logging. Kubernetes is free, with a listed plan price of free. It does not include application-level services such as databases, message buses, caches, or cluster storage systems.