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Persistent storage using Fibre Channel

OpenShift Container Platform supports Fibre Channel, allowing you to provision your OpenShift Container Platform cluster with persistent storage using Fibre channel volumes. Some familiarity with Kubernetes and Fibre Channel is assumed.

The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure. PersistentVolumes are not bound to a single project or namespace; they can be shared across the OpenShift Container Platform cluster. PersistentVolumeClaims are specific to a project or namespace and can be requested by users.

High availability of storage in the infrastructure is left to the underlying storage provider.
Additional references

Provisioning

To provision Fibre Channel volumes using the PersistentVolume API the following must be available:

  • The targetWWNs (array of Fibre Channel target’s World Wide Names).

  • A valid LUN number.

  • The filesystem type.

A PersistentVolume and a LUN have a one-to-one mapping between them.

Prerequisites

  • Fibre Channel LUNs must exist in the underlying infrastructure.

PersistentVolume Object Definition
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv0001
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  fc:
    targetWWNs: ['500a0981891b8dc5', '500a0981991b8dc5'] (1)
    lun: 2
    fsType: ext4
1 Fibre Channel WWNs are identified as /dev/disk/by-path/pci-<IDENTIFIER>-fc-0x<WWN>-lun-<LUN#>, but you do not need to provide any part of the path leading up to the WWN, including the 0x, and anything after, including the - (hyphen).

Changing the value of the fstype parameter after the volume has been formatted and provisioned can result in data loss and pod failure.

Enforcing disk quotas

Use LUN partitions to enforce disk quotas and size constraints. Each LUN is mapped to a single PersistentVolume, and unique names must be used for PersistentVolumes.

Enforcing quotas in this way allows the end user to request persistent storage by a specific amount, such as 10Gi, and be matched with a corresponding volume of equal or greater capacity.

Fibre Channel volume security

Users request storage with a PersistentVolumeClaim. This claim only lives in the user’s namespace, and can only be referenced by a pod within that same namespace. Any attempt to access a PersistentVolume across a namespace causes the pod to fail.

Each Fibre Channel LUN must be accessible by all nodes in the cluster.