Containerization is a critical component of cloud computing today. It offers a sort of create-once run-everywhere approach by allowing unrestricted access to files and processes without having to deal with complex native interfaces.

Contrary to what most people think, container technology is anything but new. The concept of containerization has existed since the 1970s and was first used to isolate application code in Unix systems. However, it was not until March 2013 that this innovation started picking up speed when it was reincarnated as Docker.

Today, containerization is facilitating agile application development. This explains why it’s a darling for small businesses as well as big tech brands, including HP and IBM. Its growth has immensely increased, especially after container security providers such as Snyk and others started offering practical solutions to container vulnerability. This was among the biggest problems that plagued containers and Kubernetes applications.

The constantly-growing popularity of containers has begged several fundamental questions, especially on the future of Virtual Machines (VMs) and how they differ from containerization. This forms the basis for our discussion in this article.

What are Virtual Machines?

A VM is an app that divides the hardware elements of your computer into several other virtual computers running as independent operating systems. A VM uses a piece of software called a hypervisor to create a virtualized environment that allows you to run what looks like several OSes.

To put it into perspective, you could install virtual versions of Windows 7, Windows 8, and Ubuntu on your actual, let’s say Window 10.

Having these virtual operating systems (known as guests) lets you test different apps breezily without portioning your real hard drive. Actually, you can boot and reboot the guest OSes in the virtual machine and they’ll behave as if they are running on a real machine.  

Major benefits of Virtual Machines

Create a bank of PCs

One of the chief reasons why Devs still rely on virtual machines is the ability to create different test environments configured for the desired operating systems. Even better, it’s possible to backup for your VMs and have a copy of each of your virtual operating systems. All that you require is a lot of hard drive space.

Test different setups

A computer with several flexible configurations offers the perfect environment for developers to run and test their applications in different scenarios. This makes virtual machines an essential tool in detecting and fixing configuration problems before releasing the application to the end user.

Better isolation and sandboxing

When developing a project inside a virtual machine, you keep everything concerning that project in a particular VM. This comes a lot in handy in preventing cross-contamination between different projects. Sandboxing the VMs also prevents them from interfering with the data on your real computer.

Disadvantages of VMs

Requires lots of space

The biggest drawback to virtual machines is that they require tons of space. Generally, a single VM demands around 30GB of storage space. Depending on what you plan to do, this space requirement may run well over a gigabyte.

Performance is dependent on host computer

While they act like separate computers, don’t forget that guest operating systems rely on your host computer’s RAM, CPU, and other components. That’s to say that a problem with the main computer will be passed on to the guest computers making them less efficient.  

What are containers?

Containers are very similar to VMs in that they also allow you to run and test your projects in a virtualized environment. However, instead of creating separate guest operating systems, containers rely on the host OS or server. Containers also, usually, share the host computer’s binary and libraries, too. What difference does this offer to the developer?

Benefits of containerization

Exceptionally light

By sharing the host computer’s binaries and libraries, containers don’t need to reproduce a separate operating system code. This makes them very lightweight. Precisely, containers are only a few megabytes in size and will, therefore, start in a couple of seconds.

Run multiple workloads from a single server

Owing to the small size of containers, it’s possible to run multiple of them on a single server than you would with VMs.

Effective isolation

Although all containers rely solely on the host computer’s OS and also share its binaries and libraries, they are self-contained and don’t interact or interfere with each other. This means that a flaw on one of the containers won’t spread to other containers. Also, in case of a malware attack on one of the containers, the information stored in the other containers won’t be affected.


Perhaps the biggest advantage of containers is their ease and speed of  replication. Thanks to their small size and self-contained package, containers can be moved from one operating system or platform to another easily and fast. For developers, the benefit here is improved agility and flexibility, which leads to a boost in productivity.

Containerization cons

May not run on certain applications

One of the biggest drawbacks of dockers is that they only favor apps that are engineered to run as discreet micro-services.

Fractured ecosystem

Although containers are based on an open-source platform, there are some container products that aren’t compatible depending on the companies behind them.

Possible loss of data

The way Docker containers are designed currently means that all data will be lost if they shut, unless you have backup. While there are ways of saving data in Docker, the process isn’t straightforward yet. 

Differences between Containers and VMs

Currently, the major difference between containers and virtual machines is size. While VMs are as large as several gigabytes, a container is a few MBs small. This has an enormous impact on your host computer’s or server’s memory in that you can run more containers than VMs at once. 

The other big difference between a virtual machine and a container is their structure. A virtual machine is a virtual computer with a self-contained operating system, but it runs on the host computer’s hardware. On the other hand, a container runs on the host’ computer’s or server’s OS. It also shares its binaries and libraries.

Are VMs going away?

We bet not. While it’s evident that containers are poised to be the future of software development, there is still a lot that needs to be done to perfect them. For instance, containers don’t offer bare-metal speeds, at least for now. Again, the issue of persistent data storage is yet to be addressed. These and the cons listed above are some of the facts that you need to understand before migrating to Docker.

On the other hand, VMs have been around for long and are mature systems- so to speak. They offer bare-metal speeds and are actually easier to manage besides being more secure.