These days, businesses function in a hypercompetitive landscape, and it’s more crucial than ever to effectively manage and deploy applications in order to remain innovative and agile.
For this reason, businesses should choose wisely when considering containers vs. virtual machines, both of which inject virtualization into their operations but offer significantly different pros and cons.
What Is a Virtual Machine?
A virtual machine is a “software computer that, like a physical computer, runs an operating system and applications,” VMWare explains. VMs create an environment that is essentially a “computer within a computer,” according to Microsoft. A VM delivers to the end user the same experience they would have on the physical computer, but a VM is “sandboxed from the rest of the system,” which means that the software inside of the VM can’t impact the computer it’s in.
The advantage is that it offers an optimal environment “for testing other operating systems including beta releases, accessing virus-infected data, creating operating system backups, and running software or applications on operating systems they weren’t originally intended for,” Microsoft notes.
Why Use Virtual Machines?
VMs have been around for decades and offer several major advantages. Several VMs can run on the same computer simultaneously, managed by a hypervisor. Each VM has its own virtual hardware, cutting down on the need for physical hardware and all the space, costs, maintenance and other demands that go along with that, Microsoft notes.
The VM’s biggest advantage over a container, according to TechRepublic’s Jack Wallen, is that it offers a full platform capable of housing several contiguous services.
“Virtual machines make perfect sense when you have a beast of a host server that can handle the load of multiple guests and you need to know that, at any given moment, you can spin up a host snapshot, should something go wrong,” he notes.
What Are Containers and How Do They Work?
Containers differ from VMs in that, while VMs virtualize hardware, containers virtualize operating systems, which can improve server use. A container “packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another,” notes container platform provider Docker. This delivers applications in a collection of smaller and more composable units.
Containers also allow software to run reliably when moving between different software environments, Docker Founder Solomon Hykes tells CIO.
“You're going to test using Python 2.7, and then it’s going to run on Python 3 in production and something weird will happen. Or you’ll rely on the behavior of a certain version of an SSL library and another one will be installed. You'll run your tests on Debian and production is on Red Hat and all sorts of weird things happen,” Hykes says, adding that security and software policies might also differ.
Because containers consist of an entire runtime environment, they cut through differences in operating system distributions. Moreover, containers are small (often, just several megabytes), while VMs can be many gigabytes in size, meaning that a server can host more containers than VMs and containers will boot up more quickly.
Containers also offer the advantage of modularity.
As CIO reports:
Rather than run an entire complex application inside a single container, the application can be split in to modules (such as the database, the application front end, and so on). This is the so-called microservices approach. Applications built in this way are easier to manage because each module is relatively simple, and changes can be made to modules without having to rebuild the entire application. Because containers are so lightweight, individual modules (or microservices) can be instantiated only when they are needed and are available almost immediately.
What to Consider When Choosing a Container vs. a VM
So how do companies choose between VMs and containers? It depends largely on the scope of an organization’s work.
Jack Wallen says the decision comes down to two questions: “Do you need a full platform that can house multiple services? Go with a virtual machine. Do you need a single service that can be clustered and deployed at scale? Go with a container.”