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Merge pull request #47674 from sftim/20240825_revise_k8s_overview 

Reorder content in Kubernetes overview section
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@ -32,65 +32,6 @@ Kubernetes project in 2014. Kubernetes combines
[over 15 years of Google's experience](/blog/2015/04/borg-predecessor-to-kubernetes/) running
production workloads at scale with best-of-breed ideas and practices from the community.
## Going back in time
Let's take a look at why Kubernetes is so useful by going back in time.
![Deployment evolution](/images/docs/Container_Evolution.svg)
**Traditional deployment era:**
Early on, organizations ran applications on physical servers. There was no way to define
resource boundaries for applications in a physical server, and this caused resource
allocation issues. For example, if multiple applications run on a physical server, there
can be instances where one application would take up most of the resources, and as a result,
the other applications would underperform. A solution for this would be to run each application
on a different physical server. But this did not scale as resources were underutilized, and it
was expensive for organizations to maintain many physical servers.
**Virtualized deployment era:** As a solution, virtualization was introduced. It allows you
to run multiple Virtual Machines (VMs) on a single physical server's CPU. Virtualization
allows applications to be isolated between VMs and provides a level of security as the
information of one application cannot be freely accessed by another application.
Virtualization allows better utilization of resources in a physical server and allows
better scalability because an application can be added or updated easily, reduces
hardware costs, and much more. With virtualization you can present a set of physical
resources as a cluster of disposable virtual machines.
Each VM is a full machine running all the components, including its own operating
system, on top of the virtualized hardware.
**Container deployment era:** Containers are similar to VMs, but they have relaxed
isolation properties to share the Operating System (OS) among the applications.
Therefore, containers are considered lightweight. Similar to a VM, a container
has its own filesystem, share of CPU, memory, process space, and more. As they
are decoupled from the underlying infrastructure, they are portable across clouds
and OS distributions.
Containers have become popular because they provide extra benefits, such as:
* Agile application creation and deployment: increased ease and efficiency of
container image creation compared to VM image use.
* Continuous development, integration, and deployment: provides for reliable
and frequent container image build and deployment with quick and efficient
rollbacks (due to image immutability).
* Dev and Ops separation of concerns: create application container images at
build/release time rather than deployment time, thereby decoupling
applications from infrastructure.
* Observability: not only surfaces OS-level information and metrics, but also
application health and other signals.
* Environmental consistency across development, testing, and production: runs
the same on a laptop as it does in the cloud.
* Cloud and OS distribution portability: runs on Ubuntu, RHEL, CoreOS, on-premises,
on major public clouds, and anywhere else.
* Application-centric management: raises the level of abstraction from running an
OS on virtual hardware to running an application on an OS using logical resources.
* Loosely coupled, distributed, elastic, liberated micro-services: applications are
broken into smaller, independent pieces and can be deployed and managed dynamically –
not a monolithic stack running on one big single-purpose machine.
* Resource isolation: predictable application performance.
* Resource utilization: high efficiency and density.
## Why you need Kubernetes and what it can do {#why-you-need-kubernetes-and-what-can-it-do}
Containers are a good way to bundle and run your applications. In a production
@ -174,6 +115,71 @@ Kubernetes:
It shouldn't matter how you get from A to C. Centralized control is also not required. This
results in a system that is easier to use and more powerful, robust, resilient, and extensible.
## Historical context for Kubernetes {#going-back-in-time}
Let's take a look at why Kubernetes is so useful by going back in time.
![Deployment evolution](/images/docs/Container_Evolution.svg)
**Traditional deployment era:**
Early on, organizations ran applications on physical servers. There was no way to define
resource boundaries for applications in a physical server, and this caused resource
allocation issues. For example, if multiple applications run on a physical server, there
can be instances where one application would take up most of the resources, and as a result,
the other applications would underperform. A solution for this would be to run each application
on a different physical server. But this did not scale as resources were underutilized, and it
was expensive for organizations to maintain many physical servers.
**Virtualized deployment era:**
As a solution, virtualization was introduced. It allows you
to run multiple Virtual Machines (VMs) on a single physical server's CPU. Virtualization
allows applications to be isolated between VMs and provides a level of security as the
information of one application cannot be freely accessed by another application.
Virtualization allows better utilization of resources in a physical server and allows
better scalability because an application can be added or updated easily, reduces
hardware costs, and much more. With virtualization you can present a set of physical
resources as a cluster of disposable virtual machines.
Each VM is a full machine running all the components, including its own operating
system, on top of the virtualized hardware.
**Container deployment era:**
Containers are similar to VMs, but they have relaxed
isolation properties to share the Operating System (OS) among the applications.
Therefore, containers are considered lightweight. Similar to a VM, a container
has its own filesystem, share of CPU, memory, process space, and more. As they
are decoupled from the underlying infrastructure, they are portable across clouds
and OS distributions.
Containers have become popular because they provide extra benefits, such as:
* Agile application creation and deployment: increased ease and efficiency of
container image creation compared to VM image use.
* Continuous development, integration, and deployment: provides for reliable
and frequent container image build and deployment with quick and efficient
rollbacks (due to image immutability).
* Dev and Ops separation of concerns: create application container images at
build/release time rather than deployment time, thereby decoupling
applications from infrastructure.
* Observability: not only surfaces OS-level information and metrics, but also
application health and other signals.
* Environmental consistency across development, testing, and production: runs
the same on a laptop as it does in the cloud.
* Cloud and OS distribution portability: runs on Ubuntu, RHEL, CoreOS, on-premises,
on major public clouds, and anywhere else.
* Application-centric management: raises the level of abstraction from running an
OS on virtual hardware to running an application on an OS using logical resources.
* Loosely coupled, distributed, elastic, liberated micro-services: applications are
broken into smaller, independent pieces and can be deployed and managed dynamically –
not a monolithic stack running on one big single-purpose machine.
* Resource isolation: predictable application performance.
* Resource utilization: high efficiency and density.
## {{% heading "whatsnext" %}}
* Take a look at the [Kubernetes Components](/docs/concepts/overview/components/)

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@ -5,8 +5,8 @@ title: Kubernetes Components
content_type: concept
description: >
An overview of the key components that make up a Kubernetes cluster.
weight: 30
card:
weight: 10
card:
title: Components of a cluster
name: concepts
weight: 20

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@ -1,7 +1,7 @@
---
title: Objects In Kubernetes
content_type: concept
weight: 10
weight: 30
description: >
Kubernetes objects are persistent entities in the Kubernetes system.
Kubernetes uses these entities to represent the state of your cluster.