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