VMs vs Containers: How to Choose the Right One

Modern software development can be complex, so anything that can improve agility, speed up processes and reduce costs is always welcome. For years, the standard solution for many professionals has been to use virtual machines (VMs) to optimize capacity.

However, in today's environment there's another option available: containerization. This technology promises to offer a number of benefits beyond those provided by traditional VM solutions. But how can you be sure if this is the right approach for you?

To answer this question, it's important to have a clear understanding of what VMs and containers are, the pros and cons of each, and how the benefits will apply to your specific requirements.

What are VMs?

Virtual machines are a collection of software that allow applications to run on virtual hardware, providing all the functionality of a complete computer without the hardware, thereby offering users greater flexibility, manageability and security. They contain everything needed to run as a full machine, including infrastructure, operating system (OS), hypervisor, bins, libraries and applications.

What are containers?

A container, meanwhile, is an isolated package within a machine. While, like a VM, it includes all the tools needed to run software, including runtime systems and applications, it still depends on an underlying OS that is shared with other containers and can’t be modified for a specific container.

Without the need for this underlying infrastructure to be included, containers are highly lightweight, yet still able to provide a fully isolated environment for software development.

The key differences between VMs and containers

VMs enable professionals to run completely separate systems using the same physical hardware, allowing users to manage multiple operating systems side-by-side, with the hypervisor managing and allocating available resources where needed, including computing power, memory and storage. This provides a high level of flexibility and control for developers.

A container, on the other hand, still requires an underlying operating system, which means that, while you can deploy multiple containers across a single physical or virtual machine, you will be more restricted to emulating a single operating system. However, because they offer everything needed to run an application in a single, lightweight package, they’re easy to deploy and scale as required.

The pros and cons of using VMs

The use of virtual machines allows developers to centralize their workloads and manage assets, operating multiple OSs without the need to invest in expensive hardware. This also means they’re easy to upgrade and expand on, as it's straightforward to configure a new VM when you need it rather than having to add additional servers. Applications and OSs can be updated without affecting the end-user experience, while they also make it easy to continue supporting legacy software.

On the other hand, they’ll require significantly more compute resources compared to containers, as each VM will need its own OS, as well as a virtual copy of all the hardware the OS requires. This means initial hardware outlays will be higher, while this can also make the development cycle more complex.

VMs can prove to be especially useful if you’re working with applications that require an OS' full functionality, or if you’ll be working across a variety of OSs.

When should you consider containers?

Meanwhile, containers are particularly useful for short-term tasks. If you need to do something that may only take a few hours, it's quick and easy to plug in a container to give you the tools you need. They can also be used when you need to minimize the number of servers you use, while still supporting multiple applications.

This is because containerization's biggest advantages include its flexibility and scalability. As they’re much less resource-intensive than VMs, you can deploy multiple containers on a single server, so you don't have to dedicate one server to each application. They can be run anywhere, at any time, and can also offer greater reliability and robustness.

In the event that an application fails, other containers housing the same application will keep running seamlessly, while any malware that infects the system will be isolated to that container, which can then be terminated.

However, it's important to understand what the potential drawbacks of relying on containers may be. Not all applications may benefit from this approach, or even be practical for containerization.

For instance, the fact that containers are reliant on an underlying infrastructure means they aren't suitable if you're working with applications across multiple operating systems. Another issue is that there's little standardization or best practice when it comes to architecture, while finding developers with the necessary skills and experience to deploy containers effectively can be a challenge. This means that, if containers are not configured effectively, they can end up costing more than you expect to fix and manage.

What about a hybrid solution?

Unless your business has a very specific focus when it comes to software development, relying wholly on either VMs or containers is likely to create issues at some point. Therefore, for most enterprises, it's likely that both technologies will have a role to play in their operations.

A hybrid solution that offers users the best of both worlds depending on the specific applications they’re working with will often be the best solution. This may, for example, involve using multiple containers on top of a virtual machine, or even placing a VM inside a single container. Doing this can offer users the security and isolation of a VM, combined with the easy setup and configuration of an application inside a container.