Docker Swarm vs. Kubernetes – Key Differences Explained

Docker Swarm and Kubernetes are tools that allow you to orchestrate container deployments in distributed environments. They both enable high availability for your workloads by letting you scale container replicas across clusters of physical compute nodes.

In this guide, we’ll explore the features of both of these container orchestration tools and discuss how they differ. This will help you make the right choice for your next app deployment. Let’s compare Docker Swarm vs Kubernetes!

What we will cover:

1. What is Docker Swarm?
2. What is Kubernetes?
3. The differences between Kubernetes and Docker Swarm
4. Docker Swarm vs. Kubernetes table comparison
5. Is Docker Swarm better than Kubernetes?

Docker Swarm is a container orchestration tool included with Docker, the popular container platform. A Docker Swarm cluster includes multiple Docker nodes, consisting of at least one manager node to control the cluster and multiple worker nodes to execute tasks. Swarm mode extends Docker by providing cluster management, container scaling, declarative configuration, and automated service discovery support. 

Regular Docker commands only work with one container at a time: Executing docker run generates a single container on your current host machine. But with Docker Swarm, you can start multiple container replicas that are distributed over a fleet of Docker hosts in your Swarm cluster. The Swarm controller monitors your hosts and Docker containers to ensure the desired number of healthy replicas is running.

The diagram below shows the Docker Swarm architecture.

Docker Swarm features

Docker Swarm includes many features required by real-world container workloads:

• Declarative configuration — You define the desired state of your deployments in config files. Swarm compares your cluster’s state and reconciles any differences.
• Scaling controls — You can declaratively scale services up or down by adding and removing container replicas, allowing you to dynamically adjust service capacity.
• Rolling updates — Swarm mode allows you to implement rolling updates for your deployments, improving safety and resiliency. You can also roll back to previous deployments to recover quickly from errors.
• Simple multi-host networking — Swarm mode provides an overlay network that ensures containers can communicate with each other, even when they’re running on different nodes in the cluster.
• Service discovery and load balancing — Each service deployed to the Swarm is assigned a reliable DNS name that facilitates simple service discovery. Swarm mode also enables easy integration with external load balancers, allowing traffic to be distributed between the nodes and containers in your cluster.

In addition to these capabilities, Swarm mode also has the benefit of simple setup and configuration. Because it’s integrated with Docker and managed through the docker CLI, it’s approachable even for developers who may be unfamiliar with concepts such as high availability and distributed computing. Docker Swarm is, therefore, a good fit for smaller teams and apps that use Docker andh now need more robust container operations in production.

Docker Swarm use cases

Docker Swarm is ideal for small to medium-sized application stacks. It provides an efficient and simple solution for deploying and managing services like databases, web apps, and backend services. Its high availability and load-balancing features make it suitable for environments that prioritize service uptime and traffic distribution. 

Docker Swarm’s integration with Docker, ease of setup, and user-friendly orchestration make it an excellent choice for development, testing, and rapid prototyping environments.

It’s important to note that although Docker Swarm is suitable for these use cases, it may have limitations for larger, more complex deployments or organizations requiring advanced customization and automation features. More robust solutions like Kubernetes might be more appropriate for such cases.

Kubernetes is a complete platform for automating container management, deployment, and scaling tasks. Originally developed at Google, it was built to scale to thousands of compute hosts while offering production-grade resilience.

Kubernetes is designed to solve all the challenges associated with cloud-native container operations. Beyond the basics of container replication and scaling, Kubernetes provides solutions for handling persistent storage, service configuration, secrets, and job processing. It’s also extensible with custom resource types and app-specific automated operators.

Kubernetes features

Some of the main Kubernetes benefits include:

• Advanced scheduling support — You can control how containers are scheduled to your nodes, such as by evaluating node capacity and neighboring containers.
• Declarative configuration — Kubernetes compares your cluster to the state declared in manifest files you write. Any changes are automatically reconciled.
• Self-healing replication — Kubernetes ensures that the number of replicas you specify will stay running. It automatically restarts and replaces failed containers, including after a node becomes unhealthy.
• Auto-scaling support — Kubernetes includes components that enable horizontal and vertical auto-scaling in response to metrics changes, ensuring your services remain highly available.
• Supports jobs and batch activities — Beyond long-lived service containers, Kubernetes is capable of hosting one-off jobs such as batch processing activities and scheduled tasks.
• Built-in networking, service discovery, and load balancing — Kubernetes includes a robust networking layer that spans all the nodes and containers in your cluster. It includes service discovery, load balancing, and HTTP routing capabilities.

Kubernetes use cases

Kubernetes is the most popular container orchestrator, with over 96% of organizations already using or evaluating it. Its extensive feature set and robust redundancy make it an appealing choice for operating containers at scale, but this also means the platform has acquired a reputation for complexity. Hence, it’s important to understand when the simpler Docker Swarm might be a more suitable choice.

Docker Swarm and Kubernetes are both designed to help you manage and scale your container deployments. However, you should consider the differences in how they achieve this before you choose between them.

1. Defining services

Both Docker Swarm and Kubernetes support declarative service configuration. Docker Swarm uses Docker Compose’s docker-compose.yml files, whereas Kubernetes relies on its own YAML manifest files. Each tool will read your config files, and then automatically create, replace, and delete containers and other resources to reconcile your cluster’s state.

You can also use imperative commands to quickly create containers without writing a YAML file. This is ideal for ad-hoc containers used for testing purposes. Docker Swarm provides the docker service create command, whereas Kubernetes has a similar kubectl create.

A key Kubernetes component is the extra abstractions it provides over basic containers: Most notably, your services run as Pods, each of which includes one or more containers. Docker Swarm doesn’t implement this concept, instead keeping containers as its basic functional unit.

2. Scaling services

Scaling is one of the main use cases for Swarm mode and Kubernetes. You can scale Swarm deployments at any time by running the docker service scale command or editing your docker-compose.yml file.

Kubernetes uses a similar mechanism, but it also supports auto-scaling. This lets your cluster dynamically adjust deployment replica counts based on actual utilization. Docker Swarm doesn’t natively implement auto-scaling so you’ll need to add your own tooling if you need this functionality.

3. High availability

Both tools accommodate high availability because you can deploy multiple replicas of your containers, across multiple independent compute nodes. This ensures your app remains accessible, even if some of the nodes fail. 

Nonetheless, Kubernetes offers slightly greater resilience through the inclusion of auto-scaling and self-healing functions. It can automatically reschedule unhealthy deployments and maintain ample capacity to match user demand.

4. Networking system

Docker Swarm and Kubernetes come with overlay network support that allows containers to reliably communicate with each other, even when distributed over multiple hosts. Service discovery features are included too, letting containers communicate using predictable DNS names.

Docker Swarm’s system is simple. It offers few features beyond the bare minimum needed for effective networking in distributed environments. Kubernetes offers more flexibility and control with support for policy-based traffic controls and customizable networking plugins, but the benefits these provide aren’t always applicable to simpler app deployment scenarios.

5. Managing services

Once you’ve created your deployments, both Docker Swarm and Kubernetes give you multiple options for managing and interacting with them. The docker service CLI commands are your main interface in Docker Swarm, whereas Kubernetes offers kubectl. These are supplemented by various third-party tools — some, like Portainer, support both Docker Swarm and Kubernetes clusters.

Monitoring is also an important part of container operations. Neither Docker Swarm nor Kubernetes comes with a built-in monitoring solution, except for access to container logs. Using integrations with popular observability suites such as Prometheus, it is easier to configure monitoring for Kubernetes,.

6. Ecosystem quality

Kubernetes is more popular than Docker Swarm, so it has a more active ecosystem. It’s the center of many operations platforms, security tools, serverless systems, and Platform-as-a-Service (PaaS) implementations. You’ll also find Kubernetes support within most IaC and CI/CD solutions.

In comparison, few third-party tools offer compatibility with Docker Swarm. Its simpler architecture isn’t designed to accommodate the degree of customization that Kubernetes enables.

7. Security, compliance, and governance

Kubernetes and Docker Swarm are intended for production-grade use. They’re both designed to support strong security with secure networking between nodes and containers. They’re also both capable of handling secret data safely.

However, Kubernetes supports more security controls, including a built-in multi-user Role-Based Access Control (RBAC) implementation and service-level network traffic policies. It also includes a robust workload security standards system that helps defend against insecure deployments. Combined with robust integrations with observability suites, Kubernetes is generally easier to govern at scale.

8. Automated load balancing

Load balancing in Docker Swarm is integrated and straightforward, thanks to a built-in routing mesh that automatically distributes network traffic to the correct service containers. Kubernetes, in contrast, offers more advanced and flexible load balancing through its Ingress and Service resources, enabling sophisticated routing rules and traffic management across pods. 

Load balancing in Docker Swarm is easier to set up, but Kubernetes offers greater control and customization for complex needs. It’s also worth noting that Docker Swarm’s simplicity has benefits and drawbacks, depending on the specific use case.

9. Cloud integrations

One of Kubernetes’ particular strengths is its strong integration with most leading cloud providers. Services like Amazon EKS and Google GKE allow you to create new Kubernetes clusters in minutes. You also benefit from two-way communication between your clusters and cloud accounts. This enables Kubernetes activity to automatically provision new storage volumes, load balancers, and compute nodes for your cluster.

Docker Swarm doesn’t provide a similar mechanism. This makes your clusters less dynamic because you need to provision any required cloud resources ahead of time and manually connect them to your Swarm nodes.

10. Configuration and learning curve

Docker Swarm is generally perceived to be simple to configure and learn. It comes bundled with Docker and includes everything you need to create clusters, attach new nodes, and deploy containers. The overall experience is similar to regular Docker and Docker Compose management.

Kubernetes is comparatively more complex, but its reputation for being difficult to configure isn’t entirely justified. Managed cloud Kubernetes services and single binary distributions like K3s mean it can actually be quicker and easier to configure a new Kubernetes environment than a Docker Swarm one. However, there is still a steeper learning curve to effectively use Kubernetes because you must understand unique concepts like Pods, ReplicaSets, and Deployments.

Here’s how Docker Swarm and Kubernetes compare across some key characteristics:

Docker Swarm and Kubernetes are both capable container orchestration tools. The right choice depends on your use case and the specific features you require.

Kubernetes is the most popular and powerful option, but its capabilities come at a cost. Docker Swarm offers a simpler setup and management experience that can make it more approachable for developers while allowing you to deploy to production using the same consistent process. Nonetheless, Kubernetes with direct cloud integrations provides the best redundancy through support for auto-scaling, which ensures your cluster’s capacity is always matched to user demand.

Kubernetes is also easy to integrate with IaC and CI/CD solutions. For these integrations, consider leveraging tools like Spacelift. Spacelift brings the benefits of CI/CD to infrastructure management. Your team can collaborate on infrastructure changes right from your pull requests. Spacelift lets you visualize your resources, enable self-service access, and protect against configuration drift.

Use Spacelift to manage your Kubernetes cluster without directly interacting with your cloud providers or IaC tools like Terraform, OpenTofu, Pulumi, or CloudFormation. For example, you can create a Spacelift stack that provisions a new AWS EKS cluster with Terraform, giving team members the ability to safely test their changes on demand.

If you want to learn more about Spacelift, create a free account today or book a demo with one of our engineers.

We’ve reviewed Kubernetes and Docker Swarm, two of the leading container orchestration technologies for managing multiple containers. 

Docker Swarm is included with Docker Engine and can be managed using the docker CLI, whereas Kubernetes is a separate solution that can run any OCI-compliant container image, including those produced by Docker.

Kubernetes has become the go-to choice for many teams using Docker containers in production. It’s a unified platform for managing cloud-native operations, including networking, storage, access control, and security. Docker Swarm has a comparatively smaller scope, but this helps to make it more approachable because there are fewer abstractions to learn.