Docker vs virtual machines

There are two main technologies for application deployment – Docker and virtual machines (VMs). Both provide options for isolating applications and resources, but they differ in their approaches and applications. In this article, we’ll give you an overview of what Docker and virtual machines have in common, how they differ, what the pros and cons of each are and what areas they’re each used in.

What is Docker?

Docker is a virtualisation solution that enables you to package and execute applications and their dependencies in containers. A Docker container is an isolated environment that contains all the components of an application, including an operating system, runtime environment, libraries and configurations. The container can be executed on any system with Docker, regardless of differences in the underlying infrastructure. Some advantages of Docker are the quick deployment of applications, simple scaling and lower resource use than other virtualisation technologies like virtual machines.

What is a virtual machine (VM)?

Virtual machines (VMs) are another way to virtualise applications. VMs are software emulations of physical computer platforms, which enable you to run multiple operating systems and applications on a single physical host. They are used for a variety of purposes, including:

• Server consolidation: Businesses can consolidate several servers on a single physical host to make efficient use of hardware and reduce costs.
• Development: Developers can use virtual machines to simulate different operating systems and development environments, in order to develop and test apps. -Isolating apps: Virtual machines make it possible to execute applications and their dependencies in isolated environments, which increases security and reduces the risk of conflict between apps. -Security: Virtual machines are often used to simulate different attack scenarios and test security concepts.

What do Docker and virtual machines have in common?

Docker and virtual machines take fundamentally different approaches, but they do have a number of things in common, particularly in the areas of portability, images and version management.

Portability

Both Docker and virtual machines are extremely portable and allow you to seamlessly execute applications and their dependencies on different systems and platforms. Docker containers can be run on any system that has Docker. And similarly, virtual machines can be deployed on different hypervisors and cloud platforms, as long as that environment supports the virtualisation technology in question.

Images

Another similarity between Docker and virtual machines is their concept of images. VM and Docker images serve as templates that describe the state and configuration of an application or operating system. In both cases, the images can be versioned and managed to track and maintain the different versions of an app or operating system. That allows developers to ensure consistent and reproducible deployments and systematically track changes made to apps and system configurations. The use of images also simplifies collaboration between development, testing and production, since developers and operations teams can use the same images to ensure that apps are deployed consistently in different environments.

Version management

Both Docker and virtual machines support the version management of images, which simplifies the development process and ensures the consistent deployment of apps. Version management enables developers to track and undo changes to images, ensuring the stability and reliability of their apps.

What are the differences between Docker and virtual machines?

While Docker and virtual machines are both used to run apps in a variety of environments, they take different approaches to doing so. We outline some of the main differences below.

Objectives

The main objective of Docker is to deploy apps and services in containers that provide isolated, portable environments. Docker focuses on improving the efficiency and scalability of apps and simplifying their deployment.

In contrast, virtual machines provide a complete virtualisation environment, in which several operating systems can be executed on a single host. Their main purpose is to enable users to create an isolated virtual environment that is independent of the underlying hardware.

Architecture

Docker containers share resources with the host operating system and its kernel. That means they have less overhead and faster startup times than virtual machines.

Virtual machines emulate a complete hardware environment and have their own operating system instance that’s independent of the host operating system and other virtual machines. This enables increased isolation but requires more resources and has longer startup times than containers.

Security

Docker containers share a kernel with the host operating system, which can pose security risks. A container image that contains errors or malware can affect the entire host.

In contrast, VMs run on their own operating system, meaning they’re more isolated. This provides a higher level of security, since attacks on a VM will generally only affect that VM.

Resources

Docker containers share resources with the host operating system, which ensures more efficient use of hardware. However, it can be difficult to isolate resource-heavy workloads.

Each VM has its own resources that are completely isolated from other VMs. This enables more precise resource management and the isolation of workloads.

Performance

Docker containers generally offer better performance and shorter startup times than VMs.

Due to their complete virtualisation environments, VMs have more overhead and longer startup times. However, they are better for resource-heavy workloads that require robust isolation.

Portability

Docker containers can easily be moved between different environments, as long as the target desktop has Docker.

VM images are less portable, since they contain an entire operating system rather than just a single app. Moving VMs between different hypervisors usually requires conversion.

What are the advantages of Docker vs virtual machines?

Due to the differences we just listed above, Docker and virtual machines each come with different advantages and are suited to different use cases.

Advantages of Docker

• Lightweight containers: Docker containers use fewer resources than VMs. They enable quick deployment of apps and efficient use of resources.
• Portability: Docker containers are portable and can be executed on different systems and cloud platforms, as long as the environment supports Docker. This makes it easier to deploy and scale apps in different environments.
• Quick deployment: Docker enables the quick deployment of apps using container technology. Developers can quickly create, start and stop containers, which speeds up development and deployment.
• Simple orchestration: Docker tools like Docker Swarm and Kubernetes make it easier to orchestrate containers. They make it possible to distribute containers among several hosts, automate scaling and ensure reliability.
• Microservices architecture: Docker is suitable for implementing microservices architectures, as it enables the isolation and deployment of individual services in containers. This improves the scalability, maintenance and flexibility of apps.

Advantages of virtual machines

• Increased isolation: Virtual machines provide more isolation between individual VMs, as each VM has its own operating system and resources. That increases security and reduces the risk of attacks and data leaks.
• Complete virtualisation: VMs allow you to run different operating systems on the same physical host, which increases the combability between different operating systems and apps.
• Legacy apps: VMs can be used to run legacy apps that require a specific operating system environment. They make it possible to run old apps on current hardware platforms without affecting the stability of the environment.
• Precise resource management: VMs offer more precise resource management, since each VM has its own resources that can be managed separately. That enables more fine-grained control over resource allocation and use.
• Safety-critical applications: VMs are well suited to running safety-critical apps that require a high degree of isolation and security. The separation of operating systems and resources minimises security risks.

Which is right for your project? Docker vs virtual machines

The decision between Docker and virtual machines depends on several factors, including the type of app, security requirements and how much flexibility you need. That’s why it’s important to weigh the advantages of each technology listed above and then choose the one best suited to the needs of your project.

Docker is particularly well suited to apps with:

• short deployment cycles
• limited resource needs for microservice architecture
• fast scalability
• physical infrastructure that’s spread out

VMs are well suited for:

• operating systems with only a single piece of physical infrastructure
• setting up operating systems with different control elements
• operating systems with specific dependencies
• special requirements for hardware resources
• legacy apps that won’t run on modern operating systems