The Kubernetes cluster is a great way to keep workloads running smoothly, but picking the correct cluster type puts Kubernetes users in a pickle. It’s challenging to understand how to create the right cluster based on users’ needs. While a single cluster technique is less expensive, a multi-cluster strategy has its own set of advantages. Let’s hear from the DevOps experts which method may fit your organization better.
A software developer often creates and maintains different apps. These apps go through various stages, such as development, testing, and production. Hence, an array of apps and environments emerges. We know each application instance is a self-contained deployment unit that can function and communicate with other application instances without requiring them. However, when it comes to launching these apps, a Kubernetes user would always be confused about choosing between a single cluster and multi-clusters.
Although Kubernetes is a flexible platform, it does not provide users with guidance on which approach to choose. DevOps experts have chimed in to assist Kubernetes users pick the best method based on their app workloads and other needs. Let us learn more.
Single Cluster Vs. Multiple Clusters
What is a Kubernetes cluster?
VMware explainsOpens a new window a Kubernetes cluster as a collection of nodes that work together to run containerized applications. Containerizing apps encapsulates an app’s dependencies as well as certain essential services. They are lighter and more adaptable than virtual machines. Kubernetes clusters make it easier to create, migrate, and manage apps in this way.
See More: How to Get Started With Kubernetes the Right Way: DevOps Experts Weigh In
One master node and a number of worker nodes make up a Kubernetes cluster. These nodes might be physical computers or virtual machines based on the cluster.
The master node is in charge of the cluster’s state, such as which apps are executing and whose container images they match. All tasks originate at the master node. It orchestrates activities such as:
- Scheduling and scaling apps
- Managing the status of a cluster
- Introducing updatesÂ
A Kubernetes cluster basically has six main partsOpens a new window : An API server, scheduler, controller manager, Kubelet, Kube-proxy, and Etcd. A Kubernetes cluster may be created and deployed on either a real or virtual system.Â
Pavan Belagatti, a developer advocate for Harness, suggests the best way to start with Kubernetes. “Get a local Kubernetes cluster up and running with Docker Desktop, Kind or Minikube. You will be able to run a single-node cluster inside a virtual machine on your laptop or the local machine.â€Â
To deploy larger applications, you need Kubernetes to be installed on your deployment machine (or machines) and use the kubectl client library to issue commands to set up and deploy applications, adds Belagatti. The Kubernetes DocumentationOpens a new window and Kubernetes QuickstartOpens a new window are two excellent resources to help you get started.
Single cluster
A single cluster is a basic infrastructure platform. Everything that needs to be executed is deployed to the current Kubernetes cluster.
Pros:
- Easy administration
- Cheap
- Efficient use of resource
Cons:
- Too many users
- Chaotic as lacks multi-tenancy
- Security issues
Multiple clusters
Multiple Kubernetes clusters make up a Kubernetes multi-cluster environment. They can be set up in various ways – within the confines of a single physical host, with a variety of hosts in the same data center, or using the same cloud provider in multiple geographies.
Pros:
- Improves scalability
- Apps isolation
- Effective cluster management
- As apps are segregated, there are fewer security issues
Cons:
- Difficult administration
- Costly
- Suboptimal use of resources
Should a developer use a single or multiple clusters?
If your requirements are small, you can get away with using a single cluster. You can easily have one large monolithic cluster that handles all of the workloads for your organization.
– Logan Donley, senior technical evangelist, CloudBees
Donley, however, warns of some risks. If you aren’t careful about access control, you can end up in a situation where those who shouldn’t have permission can access and delete resources in a particular namespace. Another risk he adds is that you can have arbitrary workloads fighting for resources with production applications.
Jason Morganson, VP of engineering at Cherre, advises on points to consider when:
- Running in a single cluster: you must be careful about resource contention. To minimize it, you need to ensure that you have your resource request and limits properly tuned. To right-size the workloads, you will need to consider the resource packing on the nodes and might need to set up separate node pools for different workloads. Finally, don’t forget about security.
- Running on multiple clusters: see how you manage access, monitoring, and deployments. Provisioning each will grow in sync with the number of clusters you have, so you will want to automate this if you plan on a large number of clusters. Keep in mind that there is an overhead cost to additional clusters.
Michael Cade, a senior global technologist at Veeam Software, thinks the better question is what we are trying to achieve. He states his experience while speaking to different organizations that use a single cluster to run an application or a particular environment, such as staging or production. “I spoke to different customers who would choose to deploy all of their applications on one larger cluster.â€Â
See More: Top Five Free Cloud Platforms to Learn Kubernetes Online
Namespaces are one of the most significant benefits of Kubernetes clusters. They allow segregating the resources within a cluster so that you can deploy multiple applications or environments within it.Â
The ease of managing a single cluster is one of the most compelling reasons to opt for deploying all your applications within the same cluster. I think a lot of this comes down to management overhead, and then the costs to run multiple or smaller amounts of clusters
– Michael Cade, senior global technologist, Veeam Software
The final call
Unless there is a compelling technical reason to isolate an application to its cluster, deploying them all to a single cluster should be ideal, advocates Donley. “Kubernetes has isolation capabilities in place. Each application can be in its namespace with role-based access control (RBAC) rules to restrict access. Network Policies can be used to prevent applications from communicating with each other unless necessary.â€
Run various environments on the same cluster, such as development, staging, and production. You may save money and minimize administrative overhead, but what is the cost of your application? Or applications? Cade says, “If you choose to have a Kubernetes cluster for each application, you will increase the number of apps you have. This will raise the cost and administrative load, as well as the danger of greater attack surface area, but it may be beneficial for your applications to be separated.â€
Cade recommends a combination of clusters. “I think we saw very much the same when it comes to virtualization of clusters. Then we saw the resurgence of hyper-converged clusters to take care of specific application use cases.†He believes there are no wrong or right answers when it comes to how big the clusters should be, although in choosing Kubernetes, it is quite easy to add and remove additional nodes to the clusters without disruption.
Conclusion
Developers should consider the approaches and decide which fits best for the workloads they are running. It’s likely that a combination of cluster approaches will work, says Morganson. This may change through the life of the applications. What is great about Kubernetes is that it allows you to tailor your clusters to meet your changing needs.
Which cluster approach do you prefer as a Kubernetes user? Let us know on LinkedInOpens a new window , TwitterOpens a new window , or FacebookOpens a new window . We’d love to hear from you!Â