Docker Swarm vs. Kubernetes: A Comparison

5 min read

Docker Swarm vs. Kubernetes: Which of these container orchestration tools is right for you?

When considering the debate of Docker Swarm vs. Kubernetes, it might seem like a foregone conclusion to many that Kubernetes is the right choice for workload orchestration. Let’s take a moment, however, to explore the similarities and differences between Docker Swarm and Kubernetes — the two preeminent container orchestrators — and see how they fit into the cloud deployment and management world.

What are containers?

In a nutshell, containers are a standard way to package apps and all their dependencies so that you can seamlessly move the apps between runtime environments. By packaging an app’s code, dependencies, and configurations into one easy-to-use building block, containers let you take important steps toward shortening deployment time and improving application reliability. Of course, to be able to use your containers most effectively, you'll need to orchestrate your containerized applications, which is where Kubernetes and Docker Swarm come in.

What is Kubernetes?

Kubernetes is developed by the community with the intent of addressing container scalability and management needs. In the early days of Kubernetes, the community contributors leveraged their knowledge of creating and running internal tools, such as Borg and Omega. With the advent of the Cloud Native Computing Foundation (CNCF) in partnership with the Linux Foundation, the community adopted Open Governance for Kubernetes. IBM, as a founding member of CNCF, actively contributes to CNCF’s cloud-native projects, along with other companies like Google, Red Hat, Microsoft, and Amazon.

Kubernetes is an open source container-management tool for those important containers and their complex production workloads. With Kubernetes, developers and DevOps teams can schedule, deploy, manage, and discover highly available apps by using the flexibility of clusters. A Kubernetes cluster is made up of compute hosts that are called worker nodes. These worker nodes are managed by a Kubernetes master that controls and monitors all resources in the cluster. A node can be a virtual machine or  physical, bare metal machine.

Pros of Kubernetes

  • Open-source community that is very active in developing the code base
  • Fast-growing KubeCon conferences throughout the year that are more than doubling attendance numbers
  • Battle-tested by big players like Google and our own IBM workloads and runs on most operating systems
  • Largest adoption in the market
  • Available on the public cloud or for on-premises — managed or non-managed offerings from all the big cloud providers (IBM Cloud, AWS, Microsoft Azure, Google Cloud Platform, etc.)
  • Broad Kubernetes support from an ecosystem of cloud tool vendors, such as Sysdig, LogDNA, and Portworx (among many others)
  • Key functionalities include service discovery, ingress and load balancing, self-healing, storage orchestration, horizontal scalability, automated rollouts and rollbacks, and batch execution
  • Unified set of APIs and strong guarantees about the cluster state

Cons of Kubernetes

  • Management of the Kubernetes master takes specialized knowledge
  • Updates from open source community are frequent and require careful patching in order to avoid disrupting workloads
  • Too heavyweight for individual developers to set up for simplistic apps and infrequent deployments
  • Often need additional tools (e.g., kubectl CLI), services, continuous integration/continuous deployment (CI/CD) workflows and other DevOps practices to fully manage access, identity, governance and security

What is Docker Swarm?

Docker Swarm is another open-source container orchestration platform that has been around for a while. Swarm —or more accurately, swarm mode — is Docker’s native support for orchestrating clusters of Docker engines. A Swarm cluster consists of Docker Engine deployed Swarm manager nodes (which orchestrate and manage the cluster) and worker nodes (which are directed to execute tasks by the manager nodes).

Pros of Docker Swarm

  • Built for use with the Docker Engine (Docker is a container platform used for building and deploying containerized applications)
  • Has its own Swarm API
  • Smoothly integrates with Docker tools like Docker Compose and Docker CLI (uses the same command line interface (CLI) as Docker Engine)
  • Tools, services, and software that run with Docker containers will also work well with Swarm
  • Is easy to install and set up for Docker environments
  • Uses a filtering and scheduling system to provide intelligent node selection, allowing you to pick the optimal nodes in a cluster for container deployment

Cons of Docker Swarm

  • Limited customizations and extensions
  • Less functionality-rich than Kubernetes
  • No easy way to separate Dev-Test-Prod workloads in DevOps pipeline

Not to confuse matters too much, but Docker Enterprise Edition now supports Kubernetes too.

Docker Swarm vs. Kubernetes: A simple head-to-head comparison

Installation and setup

  • Kubernetes: No installation required for managed offerings from cloud providers.
  • Swarm: Install it with Docker.

Scalability

  • Kubernetes: Built-in with horizontal auto-scaling.
  • Swarm: Auto-scaling groups.

Load balancing

  • Kubernetes: Discovery of services through a single DNS name. Access to container applications through IP address or HTTP route.
  • Swarm: Internal load balancers.

High availability

  • Kubernetes: Self-healing and intelligent scheduling. High availability of services through replication.
  • Swarm: Use Swarm Managers for availability controls.

Which container orchestration tool is right for you?

Docker Swarm is deployed with the Docker Engine, and is, therefore, readily available in your environment. As a result, Swarm is easier to start with, and it may be more ideal for smaller workloads. 

Kubernetes is now supported by every major cloud provider and do-it-yourself offerings like Docker Enterprise Edition, highlighting the widespread popularity of this orchestration tool. Kubernetes is more powerful, customizable, and flexible, which comes at the cost of a steeper initial learning curve. Running Kubernetes through a managed service simplifies open-source management responsibilities, which allows you to focus on building your applications.

Now that you’ve covered the differences between Kubernetes and Docker Swarm, take a deeper dive in the IBM Cloud Kubernetes Service and learn how to build a scalable web application on Kubernetes.

Learn more about Kubernetes and containers

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