VMs vs Containers | Simply Explained

Blog / VMs vs Containers | Simply Explained

So what actually is the difference between virtual machines and containers?

TL;DR Summary

Virtual Machines (VMs) and containers are both virtualization technologies that allow you to run multiple isolated applications on a single physical machine..
A container is a lightweight, portable, and self-sufficient software package that includes everything needed to run an application: the code, runtime, libraries, and system tools.

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Virtual MachinesHistorically, as server processing power and capacity increased, bare metal applications couldn't fully utilize the newfound abundance of resources. This led to the development of virtual machines (VMs). VMs are designed to run software on top of physical servers, emulating specific hardware systems to optimize resource utilization.VMs run on a hypervisor, which is a software layer enabling multiple VMs to operate on a single physical host. Hypervisors can be classified as either Type 1 (bare-metal, running directly on the hardware) or Type 2 (hosted, running on an existing operating system).Each VM contains a complete operating system (guest OS), necessary binaries, libraries, and the application code itself. This setup results in high resource usage, as each VM requires its own OS kernel and associated overhead.

Pro: VMs provide strong isolation since each VM operates independently with its own OS. This isolation extends to security and resource management.Con: Each VM includes a separate operating system image, which adds overhead in memory and storage footprint. This overhead increases complexity across all stages of the software development lifecycle, from development to production and disaster recovery.

ContainersIn contrast, a container is a lightweight, portable, and self-sufficient software package that includes everything needed to run an application: the code, runtime, libraries, and system tools.Containers avoid the overhead drawbacks of VMs by running on a container engine (e.g., Docker, Kubernetes) that operates on the host OS. As a result, containers share the host OS kernel, eliminating the need for separate OS instances for each container, which reduces memory and CPU overhead.

Containers maintain isolation from each other by using namespaces and control groups (cgroups) to manage resources and security.Pro: Containers are exceptionally lightweight—they are only megabytes in size and take just seconds to start, compared to gigabytes and minutes for a VM.Con: Security: Because containers share the host OS kernel, a security vulnerability in the kernel can potentially affect all containers running on the host.