VMs and containers are two implementations of virtualization technology. This means that both VMs and containers help to optimize how resources are used. However, these two technologies achieve that differently, and the differences between them become clear when you take a deeper look.
This post defines and explains the key differences between a container and a VM. With the information below, you can use the two solutions more efficiently while building your organization’s IT environment and adjusting workflows.
The key difference between the two solutions is in what is virtualized. A virtual machine virtualizes everything down to hardware, while a container involves virtualizing particular software layers starting from the OS level. This also means that each VM can have its own OS, and containers share an OS.
Below we review the differences between containers and VMs in detail.
In simple words, a virtual machine is an emulation of a physical machine. With VMs, an organization can use a single physical computer to run multiple machines with their own operating systems (OS) installed.
The interaction between virtual machines and physical hardware, as well as between multiple VMs in a single environment is facilitated by a hypervisor. Hypervisors allocate CPU, RAM and storage resources to particular VMs and separate VMs from one another.
A container is a prebuilt package of elements required to run a particular app or microservice. Containers originate from a different implementation of virtualization that is more lightweight and flexible than VMs. Nevertheless, containers can include runtime libraries, the code with dependencies, and even the whole OS for an application.
Containers use the host operating system’s virtualization capabilities to access the hardware resources. The use of OS virtualization means that hypervisors are not required, and containers can be run in an environment of any type, including a desktop PC, traditional IT infrastructure or cloud.
Containerization isn’t new to the IT industry. The technology was implemented decades ago. Still, the contemporary, most advanced iteration of containers was introduced in 2013 when the Docker assembly and management platform, an open-source containerization deployment, became available.
The lists of strong and weak points in a VM vs container face-off can help identify the best use cases for each of the two solutions.
As a heavy self-sufficient solution, a virtual machine can offer benefits such as:
- Secure and isolated workload: Every VM is a completely functional separate system. Due to that self-sufficiency, virtual machines are protected from attacks that exploit the vulnerabilities of other VMs hosted on the same hardware. A particular vulnerability can still be used by bad actors to access, modify or delete the data inside a VM. However, the hijacked machine does not turn into a scalable threat source as it can’t impact other VMs on the host.
- Development interactivity: Compared to a container, a VM can be developed interactively. After the basic hardware specifications for a VM are defined, that VM is not different from a barebone machine. You can install the required software on the VM manually and then create a snapshot to retain the point-in-time state of the VM. Then, a snapshot can be used to revert back to the known state of a VM.
However, building, restoring and testing a VM to ensure it runs as intended can be time-consuming. Additionally, a virtual machine can easily increase in size (up to a few gigabytes), meaning that the storage costs and space requirements also grow. To make the recovery of fully functional VMs faster and to reduce storage expenses, consider using third-party software, such as a VMware backup solution from NAKIVO.
As a lightweight package by design, a container has particular advantages over a VM:
- Known environment: You can add the required software versions, apps and runtime libraries to the container. Moreover, multiple hosted public repositories of prebuilt containers are available for download.
- Flexibility and iteration speed: Containers include only high-level software, making their iteration and modification simpler and faster.
- Portability and universality: Containers are easy to transfer and run in different locations and infrastructures, including physical, virtual and cloud environments.
The downside of containerization is related to security issues, particularly to shared host exploits. The point is that the hardware resources running the OS and higher software layers including containers belong to the same host environment. Thus, a single vulnerability in one of the containers can become a critical breach and directly disrupt the shared infrastructure.
Additionally, downloading and using the shared prebuilt containers is always a risk. A container can carry weaknesses and attract bad actors aiming to modify publicly available packages to conduct attacks.
Answering that question requires reviewing and evaluating the requirements of your organization or department.
Being lightweight and compact by design, containers can easily migrate through systems and environments of any type. Also, a container is a perfect solution for the deployment of cloud-native apps that can accelerate the development of new apps, the optimization of the existing ones, and the integration and interconnection between them. However, when considering the use of containers, keep in mind that their compatibility with the underlying OS is critical to ensure proper functioning.
The advantages of containers make them most suitable for:
- Developing cloud-native applications
- Packaging microservices
- Applying CI/CD and DevOps practices
- Accelerating the development of IT projects using the same OS
On the other hand, a virtual machine is more functional though heavier compared to a container. A VM is the most efficient way to pack and run workloads. At the same time, a virtual machine requires installing the OS, and setting libraries and applications to gain the wanted functionality, thus becoming difficult to transfer.
You can use a VM to:
- Run legacy, traditional and self-sufficient workloads
- Support isolated development cycles that can cause risks
- Build complex static infrastructures involving servers, network resources and valuable data
- Launch a fully functional OS inside a different OS (for example, Linux on a Windows machine)
Summing up the points revealed above, the key message is the following:
- A container enables an organization to optimize the use of development resources.
- A virtual machine can increase the efficiency of infrastructure resources’ utilization.
Of course, VMs and containers can be used in combination. For example, you can run containers on a virtual machine or use the appropriate solution to satisfy the needs of different departments of your organization.
VMs and containers are based on virtualization technology but are implemented differently:
- A virtual machine is a full-scale emulation of a physical computer and thus a heavyweight, multifunctional and self-efficient system. VMs are secure isolated workloads that can be deeply customized and used to build near-permanent production environments. On the other hand, virtual machines require much storage space to run and can be time-consuming to configure, restore and test.
- A container is a prebuilt package of runtime libraries, code with dependencies, and other elements (up to the OS) that are required to run an app or microservice. Being significantly lighter than virtual machines, containers are portable, flexible, and universal which makes them suitable to optimize the use of development resources. However, the reliance of multiple containers on the same hardware below the OS layer makes shared host exploits a security problem that you should take into account while using the technology.