How Are They Different?
For all their similarities, there are some key differences between VMs and containers. VMs allow one host machine to run multiple guest operating systems, and these operating systems can differ from each other. In contrast, containers run on top of a host operating system and can only be used to run applications that are compatible with that operating system.
A container is a lightweight tool that virtualizes the layers above the operating system. It isn't a full VM, and it can't communicate directly with the hardware. The container engine creates sandboxed environments that hold the binaries and libraries that are required for the applications within that container.
- Containers can be launched (and shut down) quickly.
- The storage that’s required for containers is generally much lower than VMs.
- There's a rich ecosystem of pre-made containers available for popular tools and applications.
- It's relatively easy to configure and modify containers.
- Containers can only run applications that are supported by the host OS.
- Because containers share a host, if one container is exploited, there's some risk of privilege escalation.
Some of the most popular container runtimes include Docker and containerd. Other runtimes include RKT (also known as Rocket), which is a security-focused containerization solution, and LXC, the open-source solution that has been in development since 2008. Tools like Kubernetes can also be used to automate the deployment, scaling and management of containers.
You may be wondering if containers are better than VMs. This depends on your use case. Containers are a good choice for microservices and any situation where speed and flexibility are desired. They're popular for software testing and development because people can download everything they need to run an application in a containerized form, which reduces the risk of conflicts with other software on the machine.
Containers are lightweight compared to VMs, and this makes it easier to back them up, restore them or spin up new instances on different hosts as required. Thanks to tools like Kasten, it's easy to scale Kubernetes-managed containers and have a data protection and disaster recovery (DR) plan in place.
VMs are a virtualization solution that works at a lower level than containers. They allow the guest operating system to share access to the host machine's hardware. VMs allow a host machine to run multiple operating systems, and those operating systems can run multiple programs (or even containers) themselves in the same way a normal computer would.
- VMs offer greater isolation (and therefore, security) compared to containers.
- A VM can run a different operating system than the host.
- It's possible to take snapshots of VMs at various stages of configuration and restore those snapshots or spin up multiple VMs with that configuration.
- Using VMs can be an effective way of fully utilizing server resources.
- VMs are more demanding than containers in terms of computing resources.
- Configuring a VM requires configuring the host OS and any applications needed for it as well, which can take more time than simply spinning up a container for an application.
- Backing up a VM requires more storage space than backing up a container.
- While VMs allow you to manage resource usage more effectively, their heavier footprint may impede performance.
Popular tools for creating and managing VMs include the command line only QEMU, Oracle VirtualBox and VMware ESXi. VMware and Oracle have tools that cater to home and enterprise users. Organizations that plan to make extensive use of VMs should consider not only how they'll be created and managed, but also how to automate backups and recovery.