Container vs virtual machine
Virtualization fundamentally transformed the way IT operates. Virtualisation broke the traditional (expensive, inefficient) one-to-one ratio of hardware to operating systems by allowing multiple simulated computer environments to exist on a single physical machine.
At first, virtualisation revolutionised IT through virtual machines (VMs). Each VM behaves as a fully independent computer, able to run its operating system and application code. This allows IT departments to consolidate many underused physical servers onto a smaller number of more powerful machines, significantly reducing hardware sprawl and energy costs.
Containers moved the concept of virtualization one step further. Offering a lighter-weight form of virtualisation, containers share the host machine's operating system but isolate the specific applications and their dependencies.
This makes containers incredibly fast to start and easy to move, making them ideal for cloud-based use. Overall, virtualisation allows IT teams to optimise resource usage, streamline development, enhance flexibility for disaster recovery, and ultimately drive down costs while increasing agility.
Understanding virtualisation
Virtualisation revolutionised IT efficiency by introducing a software layer between the hardware and the operating systems that run on it. This layer is known as the hypervisor, and it's the key to creating virtual machines or a container.
The hypervisor is a resource manager, allocating portions of the hardware's CPU, memory, storage, and networking to each virtual environment. It also intercepts instructions from the operating systems running inside VMs and translates them into commands the physical hardware can understand.
Modern processors often include hardware-assisted virtualisation features (such as Intel VT-x or AMD-V). These features allow the hypervisor to offload specific tasks directly to the hardware, resulting in significantly improved VM performance. While hardware-assisted virtualisation is beneficial, it's not strictly necessary; software-based virtualisation can still function effectively and efficiently.
Ultimately, virtualisation creates a layer of abstraction that makes software independent of the underlying hardware. This is the foundation of its transformative impact on IT agility and efficiency.
What is a virtual machine?
A virtual machine (VM) enables virtualisation. It's a software emulation of a physical computer system, complete with its virtual CPU, memory, storage, and network interfaces. Think of it as a simulated computer running inside another computer.
Virtual machines can be created and managed using a hypervisor, which acts like a conductor, allocating resources and ensuring smooth operation for multiple machines on a single physical machine. VMs offer a versatile tool across various computing environments:
- Personal computers (PCs): Individuals can use a virtual machine on a personal computer to run software designed for a different operating system. For instance, you might create a VM with Windows on your Mac to run specific Windows-only programs.
- On-premise servers: Businesses can leverage VMs to consolidate multiple physical servers onto a smaller number of more powerful machines. This reduces hardware costs and simplifies server management. IT departments can create VMs for specific tasks like web servers, databases, or development environments.
- Cloud computing: Cloud providers offer virtual machines as a service (IaaS), which offer incredible scalability and flexibility. Businesses can easily provision machines with the desired resources on demand, eliminating the need for upfront hardware investment. They can also scale their VMs up or down based on changing workloads.
In essence, VMs provide isolated computing environments that behave like independent computers.
This isolation allows them to run different OS and applications on the same physical machine, regardless of the location (your PC, a company server, or the cloud). This flexibility and efficiency make virtualisation a core technology in today's IT landscape.
What is a container?
While virtual machines excel at emulating entire computers, containers offer a lighter-weight and faster alternative. Unlike fully virtualised machines, containers don't simulate their hardware. Instead, they share the host machine's operating system kernel but isolate the specific application, its libraries, and dependencies needed to run. Typically, containers are orchestrated by something like Kubernetes or Docker.
This makes a container much faster to start up, and applications use fewer resources than VMs. It’s ideal to use containers for a variety of applications, including:
Microservices architecture:
Modern apps are often built as collections of small, independent services. Containers perfectly package these microservices, allowing for independent development, deployment, and scaling.
Cloud-native development:
Containers also shine in cloud environments. Their portability and fast startup times make them ideal for deploying and managing applications across cloud platforms.
Continuous integration and delivery (CI/CD):
Containers streamline CI/CD pipelines. Developers can create consistent environments for testing and deployment, regardless of the underlying infrastructure.
Standardisation and isolation:
Containers ensure that applications run consistently across different environments by bundling all their dependencies. This isolation also prevents conflicts between apps sharing the same host machine.
High-performance computing:
Containers can efficiently manage and scale parallel workloads in high-performance computing.
Containers are lightweight and efficient, to use them and managing many of them, especially at scale, can become complex. Orchestration solutions such as Docker automate deployment, scaling, and networking across multiple containers.
In short, orchestration helps manage many containers and keep programs running smoothly. Kubernetes is one example of container orchestration, and managed Kubernetes, and managed Rancher are commonly adopted to help companies manage complex technology estates that depend on containers.
Overall, containers offer a faster, more agile approach to virtualisation than VMs. Their lightweight nature and focus on isolated code make them perfect for modern development and deployment workflows, especially in cloud-based environments.
Similarity and difference
Virtual machines and containers are powerful virtualisation tools, but their approach and the resulting trade-offs differ. VMs emulate a computer system, including its virtual CPU, memory, storage, and network interfaces.
Each VM runs a complete operating system. This provides a high degree of isolation, making VMs ideal for scenarios where you must run multiple operating systems on the same hardware, support legacy applications tied to specific OS versions, or require rigorous security boundaries. However, this whole system emulation brings overhead; VMs are more prominent, slower to start, and use more resources.
Containers, on the other hand, use a lighter-weight approach. They share the host machine's operating system kernel but package the specific application along with all its necessary libraries and dependencies. This makes a container incredibly fast to start up (often in seconds) and highly portable.
Their smaller size also enables greater efficiency—you can use many more containers on a single host than VMs. Containers are well-suited for cloud-native workloads, microservices architectures, and any situation where speed, portability, and resource efficiency are crucial. At the same time, containers offer good isolation but are not as strong as VMs due to the shared kernel operating system.
Which option is better?
Virtual machines offer robust isolating qualities but are resource hungry. Yet, because each VM runs a complete and separate operating system, VMs provide the most substantial isolation. This protects code from conflicts and ensures security for highly sensitive workloads or those with strict compliance requirements. Conversely, containers can drive even more efficiency by offering a lightweight version.
Pros and Cons of Virtual Machines
VMs are a well-established technology with a wealth of management tools, support options, and a history of reliable performance, making them easier to adopt for traditional IT environments.
Simulating an entire computer system within each VM consumes considerable CPU, memory, and storage resources. This can limit the number of machines that can run on a physical machine, increasing costs.
Booting a fully virtualised operating system adds significant overhead compared to containers. This makes VMs less suitable for situations requiring rapid deployment and scaling up or down of services.
By comparison, containers share the host machine's operating system kernel, making them extremely fast to start (indeed, within seconds) and significantly smaller than virtual machines. This reduced overhead translates into lower resource costs and greater efficiency.
Comparison with containers
Packaged with all the necessary dependencies, containers are highly portable. This enables them to run consistently across different systems, simplifying development, testing, and deployment in the cloud.
The lightweight nature of containers allows for rapid application scaling. Provisioning or removing containers is far faster than doing the same with a virtual machine, making them ideal for handling variable workloads.
Conversely, sharing the host's operating system kernel means containers offer less isolation than a VM. While security measures exist, this makes them less suitable for extremely sensitive multi-tenant workloads with strict compliance boundaries.
Containers are usually dependent on the underlying host OS, restricting the types of operating systems they can run internally. This makes them less flexible than VMs for specific legacy apps.
Container technology is newer than VM technology and still evolving rapidly. Orchestration tools and best practices continue to mature, and container management can offer more complexity than traditional VM management.
Examining the applications for best fit
These computing requirements are the best fit for virtual machines:
Consolidating legacy applications:
Many older applications are built with assumptions about a specific operating system version or hardware resources. VMs create isolated environments where these dependencies are met, allowing you to run legacy applications on modern hardware and extend their lifespan.
Multi-tenant environments:
When serving multiple clients, each with its own data and application requirements, the substantial protection offered by virtual machines is paramount. VMs provide separate "walled gardens" for each client, ensuring their data and processes remain segregated, boosting security, and meeting compliance standards.
Testing and development:
It allows developers to quickly spin up test environments that mimic different operating systems, network configurations, or software versions. This streamlines experimenting with code changes, isolating testing from production systems, and ensuring software works reliably across multiple target platforms.
Disaster recovery:
The ability to replicate an entire VM with its applications and data provides a robust disaster recovery tool. Standby VMs can be activated on different hardware or geographic locations, minimising downtime, and ensuring business continuity in case of a primary site outage.
In contrast, containers are better suited to:
Microservices architectures:
Modern programs often embrace small, loosely coupled components (microservices), each handling a specific task. Containers perfectly encapsulate these microservices with their necessary dependencies, promoting scaling and updates. This aligns with agile software practices.
CI/CD pipelines:
Containers ensure consistency from setup through testing to deployment. Code is packaged in a container once and then moves through various stages of the pipeline with all its dependencies intact, eliminating configuration conflicts that often arise when deploying on different machines.
Cloud-native applications:
Built with portability in mind, containers seamlessly move across cloud platforms. They support rapid scaling by starting and stopping quickly, enabling applications to adapt automatically to changing load requirements. This resource efficiency is critical to maximising the benefits of cloud computing.
High-density deployments:
Containers' lightweight nature means a single physical server can support far more applications than a VM setup. This makes containers ideal when maximising hardware utilisation is a priority, allowing you to squeeze more value out of your existing infrastructure.
OVHcloud products
Simplified and centralised management of your Kubernetes clusters
Simplify the deployment, management, and continuous improvement of your containerised applications in a Kubernetes environment. This service simplifies multi-cluster management in Kubernetes, particularly when using multi-cloud or hybrid environments.
It can save you time and money, allowing you and your team to focus on developing containerised applications.
Free Managed Kubernetes® service to orchestrate your containers
Kubernetes® is one of the most widely-used contain orchestration tools on the market. It is used by companies of all sizes. It can be used to deploy applications, scale them up and make them more resilient - even in hybrid or multi-cloud infrastructures.
Service Managed Kubernetes® is powered by OVHcloud Public Cloud instances. With OVHcloud Load Balancers and additional disks integrated into it, you can host any kind of work load on it with total reversibility.