Containers vs VMs

Linux® containers and virtual machines (VMs) are packaged computing environments that combine various IT components and isolate them from the rest of the system. Their main differences are in terms of scale and portability.

• Containers are typically measured by the megabyte. They don’t package anything bigger than an app and all the files necessary to run, and are often used to package single functions that perform specific tasks (known as a microservice). The lightweight nature of containers—and their shared operating system (OS)—makes them very easy to move across multiple environments.
• VMs are typically measured by the gigabyte. They usually contain their own OS, allowing them to perform multiple resource-intensive functions at once. The increased resources available to VMs allow them to abstract, split, duplicate, and emulate entire servers, OSs, desktops, databases, and networks. 

Beyond the technological differences, comparing containers to VMs is a proxy comparison between emerging IT practices and traditional IT architectures. 

That depends—do you need a small instance of something that can be moved easily (containers), or do you need a semi-permanent allocation of custom IT resources?

The small, lightweight nature of containers allows them to be moved easily across bare metal systems as well as public, private, hybrid, and multicloud environments. They’re also the ideal environment to deploy today’s cloud-native apps, which are collections of microservices designed to provide a consistent development and automated  management experience across public, private, hybrid, and multicloud environments. Cloud-native apps help speed up how new apps are built, how existing ones are optimized, how they’re all connected. The caveat is that containers have to be compatible with the underlying OS. Compared to VMs, containers are best used to: 

• Build cloud-native apps
• Package microservices
• Instill DevOps or CI/CD practices
• Move scalable IT projects across a diverse IT footprint that shares the same OS

VMs are capable of running far more operations than a single container, which is why they are the traditional way monolithic workloads have been (and are still today) packaged. But that expanded functionality makes VMs far less portable because of their dependence on the OS, application, and libraries. Compared to containers, VMs are best used to:

• House traditional, legacy, and monolithic workloads
• Isolate risky development cycles
• Provision infrastructural resources (such as networks, servers, and data)
• Run a different OS inside another OS (such as running Unix on Linux)

Because we’ve supported virtualization and container development for a long time. We’ve been contributing to the Kernel-based Virtual Machine (KVM) and oVirt communities since both were founded, and we’re the second largest contributor to the Docker and Kubernetes codebases. We’re also invested in the future of these 2 technologies. Our involvement in container-native virtualization, KubeVirt, and hyperconverged infrastructure are improving how containers and VMs work together as part of the same IT system.