text: **4.3 OpenShift persistent storage**
  
  Because Plain Docker storage is not shared between nodes, it is not enough for container 
  service availability because pods might be stopped on one node and restarted on another 
  node at any time. If a database pod is stopped and restarted on another node, any stored 
  data is lost. 
  
  Kubernetes provides a framework for managing external persistent storage for containers. 
  Kubernetes recognizes a PersistentVolume resource, which can be defined as local or 
  network storage. A pod resource can reference a PersistentVolumeClaim resource to access 
  storage of a certain size from a PersistentVolume. 
  
  Kubernetes also specifies whether a PersistentVolume resource can be shared between pods 
  or if each pod needs its own PersistentVolume with exclusive access. When a pod moves to 
  another node, it stays connected to the same PersistentVolumeClaim and PersistentVolume 
  instances. Therefore, a pod’s persistent storage data follows it, regardless of the node where 
  it is scheduled to run. 
  
  OpenShift adds several VolumeProviders to Kubernetes, which provide access to enterprise 
  storage, such as iSCSI, Fibre Channel, Gluster, or a cloud block volume service, such as 
  OpenStack Cinder. 
  
  OpenShift also provides dynamic provisioning of storage for applications by way of the 
  StorageClass resource. By using dynamic storage, you can select different types of back-end 
  storage. The back-end storage is segregated into different tiers, depending on the needs of 
  your application. 