Comparing Docker Swarm and Kubernetes

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For teams building and deploying containerized applications using
Docker, selecting the right orchestration engine can be a challenge.
The decision affects not only deployment and management, but how
applications are architected as well. DevOps teams need to think about
details like how data is persisted, how containerized services
communicate with one another, load balancing, service discovery,
packaging and more. It turns out that the choice of orchestration
engine is critical to all these areas. While Rancher has the nice
property that it can support multiple orchestration engines
concurrently, choosing the right solution is still important. Rather
than attempting to boil the ocean by looking at many orchestrators, we
chose to look at two likely to be on the short list for most
organizations – Kubernetes and Docker Swarm.

Evolving at a rapid clip

To say these frameworks are evolving quickly is an understatement. In
the just the past year there have been four major releases of Docker
(1.12, 1.13, 17.03 and 17.06) with dozens of new features and a
wholesale change to the Swarm architecture. Kubernetes has been
evolving at an even more frenetic pace. Since Kubernetes 1.3 was
introduced in July of 2016 there have been four additional major
releases and no less than a dozen minor releases. Kubernetes is at
version 1.7.2 at the time of this writing with 1.8.0 now in alpha 2.
Check out the Kubernetes
changelog
to get a sense of the pace of development. *Comparing Kubernetes and
Docker Swarm is a little like trying to compare two Rocket ships
speeding along on separate trajectories. By the time you catch up with
one and get close enough to see what’s happening, the other is in a
whole different place! *

Points of comparison

Despite the challenges posed by their rapid evolution, we decided to
take a crack at comparing Swarm and Kubernetes in some detail, taking a
fresh look at new capabilities in each solution. At a high-level the
two solutions do broadly similar things, but they differ substantially
in their implementation. We took both solutions out for a test drive
(using Rancher running in AWS), got into the weeds, and compared them
systematically in these areas:

  • Architecture
  • User experience
  • Ease-of-use
  • Networking model
  • Storage management
  • Scheduling
  • Service discovery
  • Load balancing
  • Healthchecks
  • Scalability

Lots for DevOps teams to ponder

Both Swarm and Kubernetes are impressive, capable solutions. Depending
on their needs, organizations could reasonably choose either solution.
If you are new to one solution or the other, understanding the
strengths and weaknesses of different solutions, and differences in how
they are implemented, can help you make a more informed decision. Swarm
is impressive for its simplicity and seamless integration with Docker.
For those experienced with Docker, evolving to use Swarm is simple.
Swarm’s new DAB format for multi-host, multi-service applications
extends naturally from docker-compose, and the Swarm command set is now
part of Docker Engine, so administrators face a minimal learning curve.
Customers considering larger, more complex deployments will want to look
at Kubernetes. Docker users will need to invest a little more time to
get familiar with Kubernetes, but even if you don’t use all the features
out of the gate, the features are there for good reason. Kubernetes has
its own discrete command set, API and an architecture that is discrete
from Docker. For Kubernetes, the watchword is flexibility. Kubernetes
is extensible and configurable and can be deployed in a variety of ways.
It introduces concepts like Pods, Replica Sets and Stateful Sets not
found in Swarm along with features like autoscaling. While Kubernetes
is a little more complex to learn and master, for users with more
sophisticated requirements, Kubernetes has the potential to simplify
management by reducing the need for ongoing manual interventions.

About the whitepaper

Our comparison was done using Rancher’s container management framework
to deploy separate environments for Docker Swarm and Kubernetes. Rather
than focus on Rancher however, comparisons are made at the level of
Swarm and Kubernetes themselves. Whether you are using Rancher or a
different container management framework, the observations should still
be useful. Included in the paper are:

  • Detailed comparisons between Kubernetes and Swarm
  • Considerations when deploying both orchestrators in Rancher
  • Considerations for application designers
  • High-level guidance on what orchestrator to consider when

Download the free
whitepaper
for an
up to date look at Kubernetes and Docker Swarm.
As always, we
appreciate your thoughts and feedback!

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