Containers and virtual machines are two of the most popular methods for application deployment. Understanding the similarities and differences can help you to choose the right method for your project.
Containerisation is Operating System (OS) virtualisation, whereas deploying Virtual Machines (VMs) is hardware virtualisation. Popularised by the open-source project Docker, containerisation is taking the IT industry by storm and presents another option for your business’ cloud hosting.
But what exactly is it and how does it differ from virtualisation?
What is containerisation?
A container is a uniform structure in which any application can be stored, transported and run. It is named for and often compared to the standardised intermodal containers used in the shipping industry for efficient transportation.
In the software world, containerisation is an efficient method for deploying applications. A container encapsulates an application with its own operating environment. It can be placed on any host machine without special configuration, removing the issue of dependencies.
The techniques of containerisation are not new, but have shot to prominence as businesses such as Netflix and Google have used them to overcome the constraints of machine virtualisation.
What’s the difference between containerisation and virtualisation?
Both of these approaches allow you to make workloads hardware agnostic. In fact, at its simplest, containerisation is just another approach to server virtualisation. However, there are substantial differences between the two methods.
Deploying VMs, the approach we’ve all become accustomed to over the last five years, is hardware virtualisation, whereas containerisation is OS virtualisation. An application on a VM requires a guest OS and thus an underlying hypervisor to run.
By contrast, an application in a container, doesn’t require a guest OS or hypervisor. It allows an application to run in the Userspace of the OS – a segment of the computer memory that is kept separate from the critical processes of the OS kernel.
This leads to improved performance, as an application’s instructions do not have to pass through the guest OS and the hypervisor to reach the CPU. It also means that applications in containers are smaller and can be started up in seconds, compared to minutes for VMs. Significantly, container applications offer much more stability - they never hang on the host OS, like VM applications can do, which takes all VMs on the host offline.
Essentially, containerisation is a lightweight approach to virtualisation.
Although there are obvious benefits of containerisation over virtualisation, it does have its disadvantages too, and there are certainly scenarios where virtualisation is a better option. Whilst hypervisors are by no means set to become redundant, containerisation will have a growing position in the future of server hosting.