Docker and Virtual Machines (VMs) have similar objectives of isolating an application and its dependencies into a self-contained unit that can run anywhere. However, the primary difference lies in their architectural approach.
1. System Architecture: Docker utilizes a more efficient system design. It employs containers that package the application and its dependencies together, which share a common OS kernel. This makes Docker lightweight, as it doesn’t need a full OS for each application. On the other hand, every VM includes not only an application and its dependencies but also an entire guest Operating System. This makes VMs larger in size and slower to run.
1. Performance: Because Docker shares the Host OS, it’s more efficient. It can start, stop, and perform operations much faster than VMs. VMs, on the other hand, require a full OS boot and then application boot within that, making them slower in operation.
1. Density: Since Docker containers are lightweight, a host machine can run many more containers than VMs. This improves the utilization of the underlying hardware.
1. Portability: Docker containers can run on any system that runs Docker, which is easier than virtual machine platforms which usually need to emulate the underlying hardware.
1. Isolation: VMs provide stronger isolation as they have separate OS, while Docker Containers share the host’s kernel.
1. Overhead: Docker has less overhead than virtual machines as VMs require hypervisors to run the virtual machines while Docker runs directly on the host OS.
It’s important to note that choice between Docker and VMs isn’t always an either/or proposition. Both these technologies can, and often do, coexist in the same application architecture.
