The debate of containers vs. virtual machines (VMs) is one that has been quite common in the IT world in the last few years. Many folks are wondering whether they should use VMs or containers. Mostly, the question arouses during discussions within development teams.
So in this article, we’ll explore the topic of containers vs. virtual machines, and some related concepts like microservices and container orchestration. This will help you understand the pros and cons of both containers and VMs.
Virtual Machines – Consolidated, Virtualized Hardware
Let’s start by defining virtual machines, and explaining how they work.
Virtual machines were first developed to take advantage of the massive computing capacity of large servers. As servers continued to become more powerful, it became clear that simply running a single operating system (OS) on a server was a waste of resources.
VMs can run simultaneously on a single server. They run using a software layer that rests on top of the physical hardware of the server – emulating a particular hardware system. Then, a program called a “hypervisor” is used to create, manage, and run multiple VMs.
One of the biggest benefits of VMs is that multiple different operating systems can run on the same server. One server could potentially host dozens of different Linux VMs, as well as Windows VMs and other administrative operating systems.
One of the most important things to understand a VM is that it emulates every part of a “real” OS. Each VM will have its own binaries, installed applications, libraries, and services. This means VMs can easily be quite large, with sizes reaching into the gigabytes.
The primary drawback of VMs is that, since each one is self-contained, they require more memory and storage, and make software development more complex. Containers were developed to help solve this issue.
Containers – Virtualized Operating Systems for Better Agility
Containers are an alternative approach for running virtualized operating systems, and they have become very popular in the last few years.
Essentially, containers are built to interact with a physical server as well as its host OS, such as Linux or Windows. Each individual container shares this host kernel, as well as the libraries and binaries required to run the OS.
This means that containers are incredibly “light”. Hardware resources and base OS kernel are all shared. Consequently, moving them between server environments is quick and easy, making them very popular with developers. Most containers can be “spun up” in just a few minutes, and are only a few gigabytes in size.
One of the other biggest benefits of containers is that they require much less maintenance and management. Since they share an OS, only the “host” OS must be patched and maintained with bug fixes and security updates.
What Are Microservices – And How Are They Related to VMs and Containers?
The term “microservices” refers to a decentralized approach to creating new applications and software.
When you use a microservices-based software development technique, you are essentially “breaking down” all of the pieces of an application into separate, distinct services. Hence, the name.
This helps increase project portability and modularity, and allows for the re-use of many different microservices in different projects.
For example, instead of coding a brand-new payment system from the “ground up”, a company could use an existing microservice to handle credit card payments, and another microservice to handle address verification. Then, they could build other smaller, modular services to handle any services which have not already been developed.
You may be able to see where this is going. Due to the modular design and lightweight nature of microservices, containers are ideal for developing and creating a microservice-based application.
There are many benefits to doing so. First, a container can be scaled to ensure that each microservice has the appropriate amount of memory, computing power, and storage, to avoid wasting processing power.
In addition, because each container runs from the same OS, you don’t have to worry about keeping multiple VMs up to date, to ensure that microservice compatibility doesn’t break.
Finally, building and deploying containers is faster, compared to VMs. This not only allows for enhanced business agility, but also expands the ability to develop and deploy new applications much more quickly.
What Is Container Orchestration?
There are several popular container orchestration solutions out there, such as Kubernetes, Docker, and Mesos. And while their feature sets differ quite a bit, every container orchestration software is trying to accomplish the same thing.
Orchestration tools help create, upgrade, maintain, and deploy multiple containers in a single development environment.  They also enable to connect microservice containers together, allowing for rapid and intuitive application development and deployment.
Typical features of a container orchestration program include:
- Provisioning hardware resources for hosting, either on physical servers or in the cloud
- Spinning up and deploying multiple sets of containers
- Rescheduling the deployment of failed containers
- Linking containers together
- Exposing containers to other machines and APIs outside the server cluster
- Simplified scaling by adding or removing containers from the cluster
A container orchestration platform and strategy are absolutely essential for the success of any development project that is going to use microservices, or a wide variety of containers.
Orchestration makes it much easier to control the behavior and development of individual containers, ensuring a consistent development environment.
So, Which Are Better? Virtual Machines Or Containers?
The question of which is better is not really relevant. Both VMs and containers are better at different things.
VMs offer slightly better security and are ideal if you are running a full application or platform on a single operating system. However, containers have the edge if you are looking to shift to a more microservices-based development style. Use them when you want to minimize costs related to the maintenance and patching of multiple VMs.
So, in the end, there is no clear winner. The answer to which is best depends on what you want to do and how you want to do it!