Docker vs Virtual Machine (VM) | Overview.

Docker Vs Virtual Machine (VM) - Overview.

Scope:

• Intro,
• Architecture,
• Basic Definitions,
• Architecture Comparison,
• Key Differences,
• When to Use What,
• Can both Be Used Together,
• Summary Table.

Intro:

Here’s twtech comparison of Docker and Virtual Machines (VMs).

Architecture

 1. Basic Definitions

Technology	Description
Docker	A containerization platform that packages applications and dependencies into containers which share the host OS kernel.
Virtual Machine (VM)	Emulates an entire computer system (hardware + OS) using a hypervisor, allowing multiple OSes to run on one physical machine.

 2. Architecture Comparison Docker (Containers) Vs Virtual Machine

Docker (Containers)

NB:

• Shares host OS kernel
• Lightweight and fast startup

 Virtual Machine

NB:

• Each VM includes full OS
• Slower and heavier

 3. Key Differences

Feature	Docker (Containers)	Virtual Machines
Startup Time.	Seconds	Minutes
Performance.	Near-native	Overhead due to OS emulation
Isolation.	Process-level (shares kernel)	Full OS-level isolation
Size.	MBs (small images)	GBs (full OS)
OS Support.	Linux-based (Windows/macOS via VM)	Any OS (Linux, Windows, etc.)
Security.	Less isolated (shared kernel)	Stronger isolation
Portability.	High (runs anywhere Docker is supported)	Less portable
Use Case.	Microservices, CI/CD, DevOps	Legacy apps, different OS requirements, full-system emulation

 4. When to Use What

 Use Docker When:

• twtech needs fast, lightweight, scalable environments.
• twtech builds microservices or cloud-native apps.
• twtech wants consistent development environments.

 Use VMs When:

• twtech needs full OS isolation.
• twtech is running applications requiring different OS kernels.
• twtech is managing legacy apps or complex monolithic systems.

 5. Can both Be Used Together.

Yes. 

• Docker often runs inside VMs on macOS/Windows (via Docker Desktop or WSL2). 
• Many cloud platforms (e.g., AWS, Azure) run Docker containers inside VMs for better security/isolation.

Summary Table

Criteria	Docker	VM
Isolation.	Process-level	Full OS
Boot time.	Seconds	Minutes
Resource usage.	Low	High
Portability.	Excellent	Good
OS support.	Linux-native	Any OS
Use case.	CI/CD, DevOps,  cloud apps	Legacy systems, OS-specific apps