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Pro Built on several years of experience with containers
Kubernetes was built on top of several years of experience from Google working on containers in production. It's a little opinionated on how containers should work and behave, but if used correctly it can help you achieve fault-tolerant systems.
Pro Works well with modern operating systems
Kubernetes works very well with modern environments (such as CoreOS or Red Hat Atomc) which offer lightweight computing nodes that you don't have to manage, since they are managed for you.
Pro Easy to do grouping tasks
Kubernetes uses labels which are key-value pairs that are attached to objects, usually pods. They are used to specify the characteristics of an object like the version, tier, etc. Labels are used to identify objects or groups of objects according to different characteristics that they may have, for example they can be used to identify all the pods that are included in the backend tier.
Through labels it's easier to do grouping tasks for pods or containers, like moving pods to different groups or assigning them to load-balanced groups.
Pro Open Source
Kubernetes is free and open source.
Pro Supported on several PaaS
Kubernetes is currently supported by Google Compute Engine, Rackspace, Microsoft Azure, and vSphere. Work is being done to support Kubernetes on OpenShift and CloudFoundry.
Pro Great starting point for beginners
Kubernetes great for beginners who are just starting to work on clustering. It's probably the quickest and easiest way to start experimenting and learning cluster oriented development.
Con If used on an existing system, some re-organizing may be needed
Because of how opinionated Kubernetes is, it may be necessary to change some things if you decide to use Kubernetes as an orchestration tool in an existing application.
Con Cannot define containers through the Docker CLI
Kubernetes was not written for docker clustering alone. It uses a different API, configuration and different YAML definitions. So you can't use the Docker CLI or Docker Compose to define your containers. Everything has to be done from scratch.