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43 lines
2.1 KiB
Plaintext
43 lines
2.1 KiB
Plaintext
// Module included in the following assemblies:
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//
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// storage/understanding-persistent-storage.adoc[leveloffset=+1]
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[id=persistent-storage-overview_{context}]
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= Persistent storage overview
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Managing storage is a distinct problem from managing compute resources.
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{product-title} uses the Kubernetes persistent volume (PV) framework to
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allow cluster administrators to provision persistent storage for a cluster.
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Developers can use persistent volume claims (PVCs) to request PV resources
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without having specific knowledge of the underlying storage infrastructure.
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PVCs are specific to a project, and are created and used by developers as
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a means to use a PV. PV resources on their own are not scoped to any
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single project; they can be shared across the entire {product-title}
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cluster and claimed from any project. After a PV is bound to a PVC,
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that PV can not then be bound to additional PVCs. This has the effect of
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scoping a bound PV to a single namespace, that of the binding project.
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PVs are defined by a `PersistentVolume` API object, which represents a
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piece of existing storage in the cluster that was either statically provisioned
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by the cluster administrator or dynamically provisioned using a `StorageClass` object. It is a resource in the cluster just like a
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node is a cluster resource.
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PVs are volume plug-ins like `Volumes` but
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have a lifecycle that is independent of any individual pod that uses the
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PV. PV objects capture the details of the implementation of the storage,
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be that NFS, iSCSI, or a cloud-provider-specific storage system.
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[IMPORTANT]
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====
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High availability of storage in the infrastructure is left to the underlying
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storage provider.
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====
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PVCs are defined by a `PersistentVolumeClaim` API object, which represents a
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request for storage by a developer. It is similar to a pod in that pods
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consume node resources and PVCs consume PV resources. For example, pods
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can request specific levels of resources, such as CPU and memory, while
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PVCs can request specific storage capacity and access modes. For example,
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they can be mounted once read-write or many times read-only.
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