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Kubernetes how to manage storage resources, I believe that many inexperienced people do not know what to do, so this paper summarizes the causes of the problem and solutions, through this article I hope you can solve this problem.

First we will learn about Volume and how Kubernetes provides storage for containers in the cluster through Volume; then we will practice several commonly used Volume types and understand their respective application scenarios; finally, we will discuss how Kubernetes separates the responsibilities of cluster administrators and cluster users through Persistent Volume and Persistent Volume Claim, and practices the static and dynamic provisioning of Volume.

Volume

In this section, we discuss Kubernetes's storage model, Volume, and learn how to map various persistent stores to containers.

We often say that containers and Pod are temporary.

The implication is that they may have a short life cycle and are frequently destroyed and created. When the container is destroyed, the data stored in the internal file system of the container will be erased.

To persist the container's data, you can use Kubernetes Volume.

The life cycle of Volume is independent of containers. Containers in Pod may be destroyed and rebuilt, but Volume will be retained.

In essence, Kubernetes Volume is a directory, similar to Docker Volume. When the Volume is mount to all containers in the Pod,Pod, the Volume can be accessed. Kubernetes Volume also supports a variety of backend types, including emptyDir, hostPath, GCE Persistent Disk, AWS Elastic Block Store, NFS, Ceph, etc. For a complete list, please see https://kubernetes.io/docs/concepts/storage/volumes/#types-of-volumes

Volume provides an abstraction of various backend. When using Volume to read and write data, the container does not need to care whether the data is stored in the file system of the local node or on the cloud disk. To it, all types of Volume are just a directory.

We will start with the simplest emptyDir to learn Kubernetes Volume.

EmptyDir

EmptyDir is the most basic Volume type. As its name suggests, an emptyDir Volume is an empty directory on Host.

EmptyDir Volume is persistent for containers, but not for Pod. When the Pod is deleted from the node, the contents of the Volume are also deleted. However, if only the container is destroyed and the Pod is still there, the Volume is not affected.

In other words: the life cycle of emptyDir Volume is the same as that of Pod.

All containers in Pod can share Volume, and they can specify their own mount paths. Here is an example to practice emptyDir. The configuration file is as follows:

Here we simulate a producer-consumer scenario. Pod has two containers, producer and consumer, which share a Volume. Producer is responsible for writing data to Volume, while consumer reads data from Volume.

The bottom volumes of the ① file defines a Volume shared-volume of type emptyDir.

The ② producer container will shared-volume mount to the / producer_dir directory.

③ producer writes the data to the file hello through echo.

The ④ consumer container will shared-volume mount to the / consumer_dir directory.

⑤ consumer reads data from the file hello through cat.

Create the Pod by executing the following command:

Here / var/lib/kubelet/pods/3e6100eb-a97a-11e7-8f72-0800274451ad/volumes/kubernetes.io~empty-dir/shared-volume is the real path of emptyDir on Host.

EmptyDir is a temporary directory created on Host, and its advantage is that it can easily provide shared storage for containers in Pod without additional configuration. But it doesn't have persistence, and if Pod doesn't exist, emptyDir will be gone. Based on this feature, emptyDir is particularly suitable for scenarios where containers in Pod need temporary shared storage space, such as the previous producer-consumer use case.

After reading the above, have you mastered how Kubernetes manages storage resources? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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