Docker runs on hyper-v then how is it different than Virtual machines?

When Docker runs on Windows using Hyper-V as its backend, it indeed leverages virtualization technology similar to running virtual machines (VMs). However, there are significant differences in how Docker uses Hyper-V compared to traditional VMs, especially in terms of architecture, efficiency, and use case. Here's an overview of the main differences:

1. Purpose and Use Case

• Docker Containers: Docker is designed for containerization, which means it packages applications and their dependencies into containers. Containers share the host OS kernel but run in isolated user spaces. Docker on Hyper-V aims to provide a lightweight environment where containers can run in isolation while sharing the same kernel, which is optimized for deploying and scaling applications.
• Virtual Machines (VMs): VMs are designed to emulate complete hardware systems, running full instances of operating systems on top of them. Each VM includes not only the application and its environment but also a full copy of an operating system, drivers, and virtualized hardware, which makes them heavier compared to containers.

2. Architecture and Performance

• Docker Containers: Containers are more lightweight and start faster than VMs because they share the host's kernel and do not need to boot an OS for each instance. This leads to better resource utilization and efficiency, allowing more containers to run on a given hardware than VMs.
• Virtual Machines: VMs include the full OS, which consumes more resources (CPU, memory, and storage) and takes longer to start. Each VM operates independently with virtualized hardware, leading to more overhead compared to containers.

3. Isolation and Security

• Docker Containers: Containers provide process and namespace isolation, but since they share the host OS kernel, they might be considered less isolated than VMs. Docker on Hyper-V can enhance security and isolation by running containers in lightweight Hyper-V VMs, offering a compromise between traditional VMs and pure container-based approaches.
• Virtual Machines: VMs offer strong isolation by completely separating the guest OS from the host OS. This level of isolation is beneficial for running entirely different operating systems or ensuring that applications run in completely isolated environments for security or testing purposes.

4. Integration with Windows

• Docker with Hyper-V: When Docker uses Hyper-V on Windows, it typically runs a minimal Linux VM to host the Docker daemon and containers. This setup provides a near-native Docker experience on Windows, supporting Linux containers with the performance and compatibility benefits of Hyper-V virtualization.
• Traditional VMs on Hyper-V: Running traditional VMs on Hyper-V involves managing each VM's operating system, configuration, and maintenance separately. This is suitable for scenarios where full OS instances are required for compatibility, testing, or isolation beyond what containers can offer.

5. Management and Ecosystem

• Docker Containers: Docker provides an extensive ecosystem for container management, including Docker Compose for multi-container applications, Docker Swarm and Kubernetes for orchestration, and Docker Hub for sharing container images. The tooling around Docker is focused on simplifying development, deployment, and scaling of applications.
• Virtual Machines: VMs are managed through hypervisor platforms (like Hyper-V Manager) or virtualization management tools. The ecosystem around VMs is more focused on virtualized infrastructure management, including storage, networking, and VM lifecycle management.