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Storage

Storage

  • Docker containers are meant to be transients in nature which means they are meant to last only for a short period of time. They are called upon when required to process data and destroyed once finished.
  • The same is true for the data within the container. The data is destroyed along with the container.
  • To persist data processed by the containers, we attach a persistent volume to the containers when they are created.
  • OpenShift leverages the Kubernetes persistent volume framework to provision storage for a cluster.
  • Storage can be provisioned to an OpenShift cluster  using any of the plugins listed such as local, iSCSI, Fiber Channel, NFS, or from a variety of supported platforms such as GlusterFS, Ceph RDB, OpenStacks Cinder, AWS Elastic Blocks Strore, Azure Disk, Azure File, or VMWare vSphere.

  • The Storage added to the OpenShift cluster is available across the cluster as a single large pool of persistent volume resources.
  • Each project can claim the required amount of storage using persistent volume claims.
  • This storage can then be used as persistent storage within the pods in each projects.

  • To create storage, click Create Storage in the web console.
  • Select Access Mode:
    • Single User (RWO) allows the volume to be mounted as read/write by a single node only.
    • Shared Access (RWX) allows volume to be mounted by multiple nodes for read/write access
    • Read Only (ROX) allows volume to be mounted by multiple nodes but read only

  • The created storage can be attached to pods by adding to the deployment configuration

Workshop

  • For your simple-webapp-color application, try to access at URI /read_file and you will get Internal Server Error.
  • Create  a storage pool.

  • Add storage to the deployment configuration simple-webapp-color

  • You should now see the the mounted /data on the pods

  • Try to create the file with command echo "This is the test data" > /data/testfile.txt
  • And you should see:

 

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