Containers vs. VMs: What’s the Difference?

3 min read

Here’s everything you need to know to understand the containers vs. VMs debate and why containers are growing in popularity.

If you’ve only recently started learning about virtualization tools, you might wonder what the differences are in the technology conversation around containers vs. VMs. After all, containers have become a dominant force in cloud native development. It’s important to understand what they are and what they are not.

How virtualization works

Virtualization is a process whereby software is used to create an abstraction layer over computer hardware that allows the hardware elements of a single computer to be divided into multiple virtual computers.

The software used is called a hypervisor—a small layer that enables multiple operating systems to run alongside each other, sharing the same physical computing resources. When a hypervisor is used on a physical computer or server (also known as bare metal server), it allows the physical computer to separate its operating system and applications from its hardware. Then, it can divide itself into several independent “virtual machines.”

The following video provides a closer look at virtualization:

What is a virtual machine?

Virtual machines (VMs) are a technology for building virtualized computing environments. They have been around for quite a while and are considered the foundation of the first generation of cloud computing.

Simply put, a virtual machine is an emulation of a physical computer. VMs enable teams to run what appear to be multiple machines, with multiple operating systems, on a single computer. VMs interact with physical computers by using lightweight software layers called hypervisors. Hypervisors can separate VMs from one another and allocate processors, memory, and storage among them.

VMs are also known as virtual servers, virtual server instances, and virtual private servers.

What are containers?

Containers are a lighter-weight, more agile way of handling virtualization. Rather than spinning up an entire virtual machine, a container packages together everything needed to run a small piece of software. The container includes all the code, its dependencies, and even the operating system itself. This enables applications to run almost anywhere—a desktop computer, a traditional IT infrastructure, or the cloud.

Containers use a form of operating system (OS) virtualization. Put simply, they leverage features of the OS to isolate processes and control the processes’ access to CPUs, memory, and desk space.

Containers have been around for decades, but the common consensus is that the modern container era began in 2013 with the introduction of Docker.

Containers vs. VMs: What are the differences?

In traditional virtualization, a hypervisor virtualizes physical hardware. The result is that each virtual machine contains a guest OS, a virtual copy of the hardware that the OS requires to run, and an application and its associated libraries and dependencies.

Instead of virtualizing the underlying hardware, containers virtualize the operating system (typically Linux) so each individual container contains only the application and its libraries and dependencies. Containers are small, fast, and portable because unlike a virtual machine, containers do not need to include a guest OS in every instance and can, instead, simply leverage the features and resources of the host OS.

Just like virtual machines, containers allow developers to improve CPU and memory utilization of physical machines. Containers go even further, however, because they also enable microservice architectures, where application components can be deployed and scaled more granularly. This is an attractive alternative to having to scale up an entire monolithic application because a single component is struggling with load.

In the following video, Nigel Brown takes a closer look at how containers differ from VMs:

Why containers?

While there are still many reasons to use VMs, containers provide a level of flexibility that is perfect for the multicloud world. When developers create new applications, they might not know all of the places it will need to be deployed. Today, an organization might run the application on its private cloud, but tomorrow it might need to deploy it on a public cloud from a different provider. Containerizing applications provides teams the flexibility they need to handle the many software environments of modern IT.

Managing containers for multicloud

Despite the many benefits of containers, they do come with a few challenges of their own. Large enterprise applications can include a massive number of containers. Managing these containers presents some serious issues for teams. How can you have visibility on what is running and where? How do you handle crucial issues such as security and compliance? How do you consistently manage your applications?

Most businesses are turning to open source solutions such as Kubernetes. The majority of containers already run on the Kubernetes platform.

To learn about the enterprise-grade solution for Kubernetes, read about the IBM Cloud Kubernetes Service.

Be the first to hear about news, product updates, and innovation from IBM Cloud