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Containers vs. VMs: What's the Difference?

The world's leading tech companies all invest in containers. Google, Microsoft and IBM have seen the value in these systems, which enable them to pack more applications into a physical server than a virtual machine could. That said, virtual machines (VMs) aren't outdated by any means.

In fact, VMs excel in several areas where containers fail. Security presents an issue, and quality assurance is also a cause for concern in certain situations. The containers vs. VMs debate isn't as black-and-white as some might believe.

What should developers keep in mind when evaluating their virtualization tools? Between containers and VMs, which is the best option for your specific set of circumstances?

Similarities and Differences

Containers and VMs are tools for virtualization, though the process is known as "containerization" when using containers. While these systems serve a similar purpose, they're far from the same. Understanding where they diverge will help you make the best choice for your particular project.

A container system and the hypervisor system for VMs have two main differences. The container's system needs an underlying OS, which provides the basic services to all containerized applications with virtual-memory support for isolation. Hypervisors run VMs, which have their own OS with hardware VM support.

Furthermore, container systems have a lower overhead than VMs. They typically target an environment where thousands of containers are in play and provide service isolation between containers. Because of this, container services such as network support or file services can have limited resource access.

Pros and Cons of Containers

Concerning the positive aspects of containers, they have a low overhead, and you can start new containers quickly. Developers who embrace containers are often more interested in their primary advantage: the ability to pack more applications into a single physical server. Of course, containers have disadvantages as well.

As mentioned earlier, virtual machines excel in several areas where containers fail. Security is one of these areas, and it's easy to illustrate through Docker, a program for operating-system-level virtualization. Docker uses libcontainers as its technology, which accesses five namespaces to work with Linux.

That's mostly OK, but then again, you'll find many critical Linux kernel subsystems outside the container. These include Cgroups, SELinux and all devices, and file systems under /sys. Hypothetically, if an application or user has superuser privileges, they can crack the underlying operating system.

Pros and Cons of Virtual Machines

Containers are superior for running multiple copies of a single app, but VMs have better flexibility. They're ideal for running various applications, and a developer won't face restrictions in their choice of operating system. Containers tend to lock a user into a particular operating system version.

Unfortunately, VMs require a lot of system resources. They run more than just a full copy of an operating system - they also run a virtual copy of the necessary hardware. The effect this has on RAM and CPU cycles is worth consideration.

Developers should also consider the scale of their project. If they intend to run the maximum amount of a particular application on a minimum number of servers, a VM is going to fall short of a container. On the other hand, security may pose a problem, which isn't as much of an issue when using a VM.

Top Three Containers and VMs

A wide variety of containers and VMs are available for purchase. As for which of them you should choose, the answer will differ depending on your situation. You'll get an idea of your best option when you evaluate the type of work you're doing, the scale, your timeline and other influential factors.

Here are the top three containers on the market today.

  1. Docker
  2. Amazon ECS
  3. Google Kubernetes Engine

For those who prefer VMs, here are the best tools in that category.

  1. Parallels Desktop 14
  2. Oracle VM Virtualbox
  3. VMware Fusion and Workstation

It's advisable to research these products before you proceed. The correct choice for one person isn't always ideal for another. It's critical to consider a number of variables before purchase.

Making the Best Decision

Regardless of your position on the containers vs. VMs debate, each has advantages and disadvantages. Instead of thinking about the convenience of containers or the flexibility of virtual machines, consider their value within the context of your work. In doing so, you'll make the best decision for your unique situation.

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About the Author

Kayla Matthews is a tech-loving blogger who writes and edits ProductivityBytes.com. Follow her on Twitter @productibytes to read all of her latest posts! 
Published Tuesday, April 23, 2019 7:28 AM by David Marshall
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