nfs-provisioner is an out-of-tree dynamic provisioner for Kubernetes 1.4+. You can use it to quickly & easily deploy shared storage that works almost anywhere. Or it can help you write your own out-of-tree dynamic provisioner by serving as an example implementation of the requirements detailed in the proposal. Go here for a demo of how to use it and here for an example of how to write your own.
It works just like in-tree dynamic provisioners: a StorageClass object can specify an instance of nfs-provisioner to be its provisioner like it specifies in-tree provisioners such as GCE or AWS. Then, the instance of nfs-provisioner will watch for PersistentVolumeClaims that ask for the StorageClass and automatically create NFS-backed PersistentVolumes for them.
This repository houses community-maintained external provisioners plus a helper library for building them. Each provisioner is contained in its own directory so for information on how to use one, enter its directory and read its documentation. The library is contained in the lib directory.
An external provisioner is a dynamic PV provisioner whose code lives out-of-tree/external to Kubernetes. Unlike in-tree dynamic provisioners that run as part of the Kubernetes controller manager, external ones can be deployed & updated independently.
External provisioners work just like in-tree dynamic PV provisioners. A StorageClass object can specify an external provisioner instance to be its provisioner like it can in-tree provisioners. The instance will then watch for PersistentVolumeClaims that ask for the StorageClass and automatically create PersistentVolumes for them.
Managing storage is a distinct problem from managing compute. The PersistentVolume subsystem provides an API for users and administrators that abstracts details of how storage is provided from how it is consumed. To do this we introduce two new API resources: PersistentVolume and PersistentVolumeClaim.
A PersistentVolume (PV) is a piece of storage in the cluster that has been provisioned by an administrator. It is a resource in the cluster just like a node is a cluster resource. PVs are volume plugins like Volumes, but have a lifecycle independent of any individual pod that uses the PV. This API object captures the details of the implementation of the storage, be that NFS, iSCSI, or a cloud-provider-specific storage system.
A PersistentVolumeClaim (PVC) is a request for storage by a user. It is similar to a pod. Pods consume node resources and PVCs consume PV resources. Pods can request specific levels of resources (CPU and Memory). Claims can request specific size and access modes (e.g., can be mounted once read/write or many times read-only).
While PersistentVolumeClaims allow a user to consume abstract storage resources, it is common that users need PersistentVolumes with varying properties, such as performance, for different problems. Cluster administrators need to be able to offer a variety of PersistentVolumes that differ in more ways than just size and access modes, without exposing users to the details of how those volumes are implemented. For these needs there is the StorageClass resource.
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