rawblock
Summary and Key concepts
Summary:
This article explains how to use Portworx CSI Driver for creating and managing raw block devices in Kubernetes or OpenShift environments. It highlights support for both file and block volume types and describes how to create a PersistentVolumeClaim (PVC) with block volume mode for applications that require raw block devices. The article walks through creating a PersistentVolumeClaim
and deployment YAML configurations for using raw block storage with a Kubernetes deployment. Specific instructions for applying these configurations differ slightly based on the environment, whether using kubectl
or oc
for OpenShift.
Kubernetes Concepts:
- PersistentVolumeClaim (PVC): A request for storage by a user.
- VolumeMode: By setting a Block mode in PVCs allows raw block devices to be requested instead of file-based volumes.
- StorageClass: Defines the class of storage to be used for PVCs.
- Deployment: A Kubernetes object that manages a replicated application, updating and scaling based on specifications.
- VolumeDevices: Used to mount raw block devices inside containers.
Portworx Concepts:
- Portworx CSI Driver: Implements the CSI specification to expose Portworx storage as file or block volumes in Kubernetes.
- CSI Enabled Storage Classes: Preconfigured storage classes for CSI in Portworx.
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.
Currently, only ReadWriteOnce PVCs can be created with the block volume mode.
Create and use raw block PVCs
-
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 -
Apply the
raw-block-pvc.yaml
spec to create the raw block PVC: -
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 -
Apply the
raw-block-deployment.yaml
spec to create the deployment utilizing our raw block PVC: