When it comes to efficient utilization of computer resources, both Docker containers and Virtual Machines (VMs) can help you to get the most out of them. Although Docker containers are relatively new to the market, however, in the recent few years, they have been growing tremendously. Virtual Machines (VMs) have always been one of the favorites for data centers of all sizes. So why the hype of containers? Before you decide on the best solution, you need to understand the concept of docker vs virtual machines very concisely.
If you are expanding and looking out for the best solution to host your services either on bare metal servers or cloud, then it is important for you to understand the roles that they play. In addition to this, you also need to understand what benefits they bring along with them and which one is the best for your requirements with respect to the cost, ease of management, portability, security, and several other factors.
In this article on Docker Vs Virtual Machines (VMs), we will try to walk you through all these aspects so that at the end, you will be well-equipped with all the necessary information.
Before we start with the discussion, make sure you understand the basics of Docker and container in general. You can refer to our articles on What is Docker? Here are the complete free Docker Tutorials carefully crafted by industry experts.
Basics of Virtual Machines and Docker Containers
What are Virtual Machines (VMs)?
A Virtual Machine (VM) can be considered as an emulation of a complete computer system. In simpler words, it allows you to run what seems to be a collection of many computers together in a single computer system. All of these so called computers running inside a system are isolated from each other. This means that the processes running inside one VM does not affect the other.
Each VM provides its own operating system and the applications running inside each of them share the hardware resources of the underlying host machine. In fact, they can even share resources from a pool of host servers connected through a network. The Virtual Machines require their own instances of operating systems and the hardware that they utilize are virtualized. A VM is simply a computer file or a software that is more commonly know as a guest or image OS which is created without any computing environment.
Why should we use Virtual Machines?
Virtual Machines are created to perform those tasks which if run on the host OS, would cause security risks. VMs eliminate these risks because they are isolated from the underlying host and other VMs running on the host. Hence, the software or processes running inside the VM would not interfere with other processes running outside it. Thus, implementing tasks such as fiddling around with virus-infected data, OS testing, OS backups, creating beta releases, etc. can be done inside a Virtual Machine.
A host machine can have multiple VMs running inside it. Some of the key files running inside a Virtual Machine are the NVRAM file, log file, virtual disk file, and configuration file. Virtual Machines are quite useful in server virtualization as well. Here, a physical server is divided into one or more unique and isolated servers. Each of these servers is allowed to run its own instances of operating systems independently. Each of them provides their own virtual hardware consisting of CPUs, network interfaces, hard drives, memory, etc.
Categories of Virtual Machines
Predominantly, Virtual Machines are divided into two broad categories. These are –
- System Virtual Machines – It provides a platform that allows multiple VMs each with their own copy of OS to share the physical hardware of the underlying host. This virtualization technique is provided by a software layer called hypervisor which executes at the top of the host infrastructure.
- Process Virtual Machines – Process Virtual Machines provide a virtual programming environment that is platform-independent. They are designed to abstract the details of the underlying hardware and OS. They allow the programs to run in the same manner in any given platform.
What are the benefits of Virtual Machines?
The benefits of using Virtual Machines are –
- All the resources of the underlying host infrastructure are available to the applications running inside the VMs.
- They provide established management and security tools.
- The processes running inside the VMs are isolated from those running inside other VMs and also the underlying host.
- Tasks that possess high-security risks such as handling virus-infected data, creating backups of OS, testing OS, etc. can be performed easily without any risk.
Popular Virtual Machine Providers
Some of the most popular providers of Virtual Machines are –
Drawbacks of Virtual Machines
Although it may sound efficient that many Virtual Machines can be run on a single host, thus allowing efficient utilization of the underlying host’s hardware. However, it is not the case. It leads to unstable performance and eats up a huge chunk of the system resources. This is so because each VM will have its own kernel, file system, libraries, dependencies, etc. Some other drawbacks of Virtual Machines include long boot uptime, not-so-efficient hypervisors, etc.
All these problems and flaws were solved with the inception of Containers.
What are Containers?
Instead of virtualizing the underlying host systems hardware infrastructure, Containers virtualize the operating system. Containers provide isolated working environments and runs on top of the host infrastructure and OS. Just like VMs, a host machine can run multiple containers isolated from each other. These containers share the host OS kernel, binaries, libraries, etc. Each container has their own userspace but share the same kernel space.
Why should we use Containers?
As discussed above, the containers share the OS resources such as libraries, binaries, etc. The shared components are read-only. This sharing of resources reduces the need to reproduce the OS code repeatedly. This means that multiple container workloads can run efficiently with a single OS installation.
This makes containers very light in weight. Typically, the size of a container is a few megabytes. In contrast, the size of a Virtual Machine can go up to a few gigabytes. Moreover, containers take just a few seconds to start. As compared to VMs, containers simply require an underlying OS, supporting libraries, and minimal system resources to run programs inside them. In simpler terms, this means that we can easily run 2 to 3 times more programs or applications inside a single-host server with multiple containers running on it. Moreover, containers allow us to create a fully packaged, isolated, secured, and portable environment for all the phases of the software development lifecycle including development, testing, and deployment.
Types of Containers
Having discussed how a container works, let’s try to understand the two most common types of containers. These are –
- Linux Containers (LXC) – Linux uses namespaces and control groups to achieve OS-level virtualization which allows us to run multiple Linux operating systems in a single host. All these Linux systems are isolated from each other. In fact, LXC was the first type of containerization concept.
- Docker – Docker made several changes to LXC containers and started a project which allows us to build single-application containers making them flexible and portable. Later, it transformed into its own container runtime environment called runc. Docker uses containerd (daemon server) and runc at different levels to achieve the concept of containerization. In simpler terms, Docker is an open-sourced platform that provides tools and utilities to build, run, and ship containers. With the help of simple commands, you can quickly spin up a container in just a matter of seconds.
What are the benefits of Containers?
Some of the highlighting benefits of containers are –
- They promote reduced management of resources, allowing developers to easily develop applications in pre-built, packaged, and isolated working environments.
- Containers are very light in weight which leads to a reduced size of application snapshots compared to VMs.
- It’s just a matter of seconds to spin up a container. In contrast to this, VMs takes a few minutes to start.
- Security updates are simplified and occur very less frequently.
- The code to transfer, migrate, or upload workloads is quite less.
Popular Providers of Container Technology
The popular container technology providers available today are –
Use Cases of Containers Vs Virtual Machines
Virtual Machines and Container have their own advantages, disadvantages, and use-cases. There is no hard and fast rule that you need to use a specific one. It totally depends upon your use case and requirements. However, the most common scenarios where each one of them are used are –
- Virtual Machines are used when you need to give priority on security more than resource-utilization. It is used when you need to manage a wide variety of OS or you need to use all of the underlying host’s OS functionalities and resources. Complex application with huge requirements are better ti run in bare-metal servers implementing VMs than containers.
- The best use case of running containers is when you want to run a maximum number of programs or applications which needs to be run in as less number of servers as possible.
The Difference – Docker Vs Virtual Machines
Now that we have discussed all the ins and outs of docker containers and virtual machines, less dive deep into their differences.
| Feature | Container | Virtual Machine |
|---|---|---|
| Isolation | Does not provide as secure a boundary as in the case of Virtual Machines. The level of isolation is quite less. | Provides complete isolation from host OS and other VMs. |
| OS | Only the userspace of the OS is different. The kernel of the OS is shared. | Runs a complete OS including the Kernel. |
| Load Balancing | An orchestrator can be used to automatically start or stop containers or assign tasks to other working containers. | In the case of a failover cluster, it moves running VMs to other nodes. |
| Fault Tolerance | If any cluster node fails, then the orchestrator can automatically create a new node and assign the relevant jobs. | VMs on failure restarts on a new server. |
| Persistent storage | Can use volumes for persistent storage. Volumes use mounted directories. | Can use a virtual hard disk. |
| Deployment | Can use Docker to create and deploy containers using command line. | Can deploy VMs using hyper-v manager or windows admin center. |
| Guest compatibility | It runs on the same OS version of the host. | Can run any OS inside VM. |
| Startup times | It takes just a few seconds to start up. | It starts up in few minutes. |
| Weight | It is very light in weight, typically just a few megabytes. | They are very large in size with upto a few gigabytes. |
| Level of virtualization | They provide OS-level virtualization. | They provide hardware-level virtualization. |
Container Vs Virtual Machine – Which is better?
According to research by Gartner, by 2023, around 50% of all the top IT companies will adopt Docker for their day-to-day IT services. Moreover, the revenue generated by the container service provider platform Docker will see a staggering increase from a mere $465.8 million in the year 2020 to $944 million in the year 2024. However, it wouldn’t be fair to compare docker with virtual machines as they are both intended for different uses. In general, for testing purposes, we can use Docker containers and for tasks that require complete isolation for security risks, we can use Virtual Machines.
Wrapping Up!
To conclude, in this article we have thoroughly discussed what docker containers and virtual machines actually are, how they work, their advantages, disadvantages, types, etc. In the end, we discussed docker vs virtual machines in detail with respect to several features. This concludes the “docker vs virtual machines” article.
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