Multiple containers can run a single host without a need for a new VM. They access the same OS kernel. Containers work on bare-metal systems.
As mentioned above, application containers bundle runtime components necessary to run the desired software.
Application containers consume less resources compared to applications deployed on virtual machines because containers share resources without a full operating system. The container engine deploys these bundles on host.
The most common app containerisation technology is Docker, specifically the open source Docker Engine and containers based on universal runtime.
Docker Swarm is a clustering tool. IT administrators and developers manage docker nodes as a single virtual system using it.
Application containerisation works with microservices and distributed applications. Each container operates independently and uses minimal resources from the host. Scaling up is easy to meet business growth. Containers encourage flexibility. Developers can quickly make desired variations from the standard image and update the image to run on host.
Virtual server abstracts the operating system and application from the underlying hardware or resources. A layer resides between server hardware and application and services. Application runs on its own version of an OS and dependency. For each different OS, it needs a separate virtual server and it also consumes more resources and requires more licenses as well. Refer below image.
Containers are an abstraction at the app layer that packages code and dependencies together. Multiple containers can run on the same machine and share the OS kernel with other containers, each running as isolated processes in user space. Containers take up less space than VMs, can handle more applications and require fewer VMs and Operating systems. Refer below image.
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Containerisation is great but they do not pass all hurdles. If you really want to understand how containers work, you have to understand its limitations as well.
Containers are popular over the past few years. It doesn’t mean it fits for all your workloads. It does have certain limitations.