Docker vs Virtual Machines: The Comparison You Need

When someone talks about virtualization, the two most popular options (as of today) are virtual machines (VM) and Docker. It is true that both have some similarities but VMs have advantages over Docker and Docker has other advantages over VMs.

The choice of one or the other depends on your needs. Therefore in this post we will explain their differences and advantages so that you can decide for one or the other depending on your needs.

What is Docker?

Docker is a platform that has several functions such as creating, shipping and running distributed applications. What Docker allows developers to do is to be able to package an application and its dependencies into a single unit.

This unit is known as a container. Containers are lightweight and can run anywhere regardless of infrastructure or resources.

How Docker Works

The way Docker works is by containers. These containers (as the name suggests) contain everything an application needs to run. Among the things it needs for its execution we can find the application code, the libraries it needs, the environment variables and the runtime.

Each container is independent of other containers. That is, each container has its own resources, its own file system and its own network.

Docker containers are built from snapshots (states) of containers. These snapshots are stored in registries (e.g. Docker Hub). This way they can be easily extracted and run on any Docker machine.

This way of storing them allows the distribution and deployment of applications to be neither complex nor difficult since everything the application needs to run is in the image and can be installed with a single command.

What are Virtual Machines?

Virtual machines, also known by their abbreviation VMs, are software simulations of hardware. They allow you to run multiple operating systems on the same physical machine.

Each VM operates independently from other VMs: they also have their own OS, their own applications and their own files.

How Virtual Machines Work

Virtual machines work by running a hypervisor. A hypervisor is software that can create virtualized environments on which operating systems can run.

This hypervisor is like an intermediate layer between the physical machine and the virtual machine. It gives the virtual machine access to resources (memory, storage, cpu) of the physical machine.

Although the virtual machine is running inside the physical machine, it runs independently with its own OS, its own resources and applications.

Each virtual machine also runs independently from other VMs that may be running on the physical machine and have no connection whatsoever (unless configurations are changed).

Docker vs Virtual Machine Advantages and Disadvantages

Having clear what Docker and VMs are and how they work, let’s go deeper into their differences. In the following sections we will compare the differences between Docker and virtual machines in terms of resource utilization, portability, security, deployment and cost.

Resource Utilization

One of the advantages of Docker over virtual machines is resource utilization. Since Docker containers share the resources of the host system, they need fewer resources than VMs to run. Moreover, Docker containers are significantly lighter than VMs making them more resource efficient.

On the other hand, VMs must run on a supervisor making them require more resources to run. So VMs are a worse choice over Docker in terms of resource utilization.

Portability

Docker containers, as mentioned before, are self-contained. This means that since each container contains everything it needs to function, it is easy to move them from one host to another allowing for greater flexibility at the deployment and scaling level.

If we talk about virtual machines, although they are also portable, they are not as portable as Docker containers. This is because their size and dependencies make them more difficult to move. In the event of a failure or a required migration, this could be considered a major disadvantage compared to Docker.

Security

Because containers are completely isolated from each other and from the host system, they provide a higher level of security compared to what a virtual machine can offer.

This reduces the risk of potential security breaches and more. This extra isolation of Docker allows for more efficient resource utilization than a virtual machine. So it is also very unlikely that a Docker container will affect the performance of others.

On the virtual machine side, yes, they are secure but they are more prone to security breaches compared to Docker. The biggest problem is that if one virtual machine has a security breach, it could also affect the security of other VMs on the same physical machine since they all run on top of it.

Deployment

Docker offers an easier deployment process compared to VMs. Again, as they are completely self-contained containers they have an extra ease when deploying, moving or upgrading.

If we talk about VMs, they are more complex to deploy mainly because they require more configurations and management than Docker. This can cause more inefficiency and a possible increase in downtime.

Cost

Finally, cost is another key point when choosing Docker or VM. Both are cost-effective but Docker is usually preferred because it is more affordable due to its resource efficiency and deployment processes.

Another cost advantage is the physical machine resources. That is, Docker usually requires fewer resources than VM, thus reducing its costs even more.

Virtual machines are still profitable, just not as profitable as Docker can be. As we mentioned before, VMs tend to use more resources of the physical machine, so you may need a computer with more resources and this again would mean a higher cost.

Conclusion

For the final words, both Docker and virtual machines have advantages and disadvantages.

It is true that in the comparison Docker has come out ahead of virtual machines, but this does not mean that virtual machines are bad or useless. It all depends on the requirements needed.

If one of your requirements is to have a fast and efficient deployment, Docker containers should be your choice. This also allows you to easily manage and scale your applications.

If your requirements include a high level of security, go for Docker again. The isolation between containers provides an extra level of security.

On the other hand, if you are an organization that needs to virtualize a complete operating system on complete hardware, virtual machines should be the option of choice. Especially if a requirement is to run multiple applications on the same machine.

Finally, both are valid solutions, but the requirements must be well known before making the choice. Regardless of your choice, be sure to research the capabilities of each based on your needs.