Docker Swarm vs. Kubernetes: A Comparison

5 min read

By: Chris Rosen

Docker Swarm vs. Kubernetes: Which is the right container orchestrator 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 these 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 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 scaling 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), 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-orchestration tool for those important containers and their complex production workloads. With Kubernetes, developers 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.

Pros:

  • Open-source community that is very active in developing the code base: https://kubernetes.io/

  • 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

  • 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

  • Broad Kubernetes support from cloud tool vendors, such as Sysdig, LogDNA, and Portworx (among many others)

  • Key capabilities include service discovery and load balancing, self-healing, storage orchestration, horizontal scaling, automated rollouts and rollbacks, and batch execution

Cons:

  • 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

For more of an overview of Kubernetes, see our video, "Kubernetes Explained":

What is Swarm?

Swarm is another open-source orchestrator that has been around 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 manager nodes—which orchestrate and manage the cluster—and worker nodes—which are directed to execute tasks by the manager nodes.

Pros:

  • Built for use with the Docker engine (Docker is a container platform used for building and deploying containerized applications)

  • Has its own API

  • Uses the same CLI as Docker engine

  • 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:

  • Limited customizations and extensions

  • Less functionally rich as Kubernetes

  • No easy way to separate Dev-Test-Prod workloads

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

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

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Which is right for you?

Docker Swarm is deployed with the Docker engine, therefore is readily available in your environment. As a result, Swarm is easier to start with and 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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