When people talk about containers, they usually mean application containers. Docker is automatically associated with application containers and is widely used to package applications and services. But there is another type of container: system containers. Let us look at the differences between application containers vs. system containers and see how each type of container is used:
|Application Containers||System Containers|
The Low-Down on Application Containers
Application containers are used to package applications without launching a virtual machine for each app or each service within an app. They are especially beneficial when making the move to a microservices architecture, as they allow you to create a separate container for each application component and provide greater control, security and process restriction. Ultimately, what you get from application containers is easier distribution. The risks of inconsistency, unreliability and compatibility issues are reduced significantly if an application is placed and shipped inside a container.
Docker is currently the most widely adopted container service provider with a focus on application containers. However, there are other container technologies like CoreOS’s Rocket. Rocket promises better security, portability and flexibility of image sharing. Docker already enjoys the advantage of mass adoption, and Rocket might just be too late to the container party. Even with its differences, Docker is still the unofficial standard for application containers today.
System Containers: How They’re Used
System containers play a similar role to virtual machines, as they share the kernel of the host operating system and provide user space isolation. However, system containers do not use hypervisors. (Any container that runs an OS is a system container.) They also allow you to install different libraries, languages, and databases. Services running in each container use resources that are assigned to just that container.
System containers let you run multiple processes at the same time, all under the same OS and not a separate guest OS. This lowers the performance impact, and provides the benefits of VMs, like running multiple processes, along with the new benefits of containers like better portability and quick startup times.
Useful System Container Tools
Joyent’s Triton is a Container as a Service that implements its proprietary OS called SmartOS. It not only focuses on packing apps into containers but also provides the benefits of added security, networking and storage, while keeping things lightweight, with very little performance impact. The key differentiator is that Triton delivers bare-metal performance. With Samsung’s recent acquisition of Joyent, it’s left to be seen how Triton progresses.
Giant Swarm is a hosted cloud platform that offers a Docker-based virtualization system that is configured for microservices. It helps businesses manage their development stack, spend less time on operations setup, and more time on active development.
LXD is a fairly new OS container that was released in 2016 by Canonical, the creators of Ubuntu. It combines the speed and efficiency of containers with the famed security of virtual machines. Since Docker and LXD share the same kernels, it is easy to run Docker containers inside LXD containers.
Ultimately, understanding the differences and values of each type of container is important. Using both to provide solutions for different scenarios can’t be ruled out, either, as different teams have different uses. The development of containers, just like any other technology, is quickly advancing and changing based on newer demands and the changing needs of users.
Monitoring Your Containers
Whatever the type of container, monitoring and log analysis is always needed. Even with all of the advantages that containers offer as compared to virtual machines, things will go wrong.
That is why it is important to have a reliable log-analysis solution like Sumo Logic. One of the biggest challenges of Docker adoption is scalability, and monitoring containerized apps. Sumo Logic addresses this issue with its container-native monitoring solution. The Docker Log Analysis app from Sumo Logic can visualize your entire Docker ecosystem, from development to deployment. It uses advanced machine learning algorithms to detect outliers and anomalies when troubleshooting issues in distributed container-based applications. Sumo Logic’s focus on containers means it can provide more comprehensive and vital log analysis than traditional Linux-based monitoring tools.
About the Author
Twain began his career at Google, where, among other things, he was involved in technical support for the AdWords team. His work involved reviewing stack traces, and resolving issues affecting both customers and the Support team, and handling escalations. Later, he built branded social media applications, and automation scripts to help startups better manage their marketing operations. Today, as a technology journalist he helps IT magazines, and startups change the way teams build and ship applications.
Application Containers vs. System Containers: Understanding the Difference is published by the Sumo Logic DevOps Community. If you’d like to learn more or contribute, visit devops.sumologic.com. Also, be sure to check out Sumo Logic Developers for free tools and code that will enable you to monitor and troubleshoot applications from code to production.