Raw block devices in Rancher

The Portworx CSI Driver supports both File and Block volume types in Kubernetes PVCs. While file has more supported features, block support for ReadWriteOnly PVCs was added in Portworx Enterprise in version 2.8.0.

Use cases for Raw Block Devices

If your application has a requirement to consume a raw block device as opposed to a mounted filesystem, this is a perfect use case for Portworx CSI Raw Block devices.

note

Currently, only ReadWriteOnce PVCs can be created with the block volume mode.

Create and use raw block PVCs

In this example we are using the px-csi-db storage class out of the box. Please refer CSI Enabled Storage Classes for list of available CSI enabled storage classes offered by Portworx.

1. Create a PVC spec that references the portworx-csi-sc as seen below in a YAML file named raw-block-pvc.yaml:

   kind: PersistentVolumeClaim
   apiVersion: v1
   metadata:
      name: px-csi-raw-block-pvc
   spec:
      volumeMode: Block
      storageClassName: px-csi-db
      accessModes:
        - ReadWriteOnce
      resources:
        requests:
          storage: 2Gi

2. Apply the raw-block-pvc.yaml spec to create the raw block PVC:

   kubectl apply -f raw-block-pvc.yaml

3. Create a deployment SPEC that references the above raw block PVC in raw-block-deployment.yaml:

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: ioping
   spec:
     selector:
       matchLabels:
         app: ioping
     strategy:
       rollingUpdate:
         maxSurge: 1
         maxUnavailable: 1
       type: RollingUpdate
     replicas: 1
     template:
       metadata:
         labels:
           app: ioping
           version: "1"
       spec:
         containers:
         - name: ioping 
           image: hpestorage/ioping 
           command: [ "ioping" ] 
           args: [ "/dev/xvda" ] 
           volumeDevices: 
           - name: raw-device 
             devicePath: /dev/xvda 
         volumes:
         - name: raw-device
           persistentVolumeClaim:
             claimName: px-csi-raw-block-pvc

4. Apply the raw-block-deployment.yaml spec to create the deployment utilizing our raw block PVC:

   kubectl apply -f raw-block-deployment.yaml