4.4.5.3. Storage Class

In Kubernetes, a StorageClass provides a way for administrators to describe the “classes” of storage they offer.
For NVMesh, different StorageClasses could describe different type of volumes that will be created by the NVMesh backend. (e.g different RAID Levels).

Let’s look at an example of a StorageClass yaml and then describe the fields relevant to NVMesh and their options.
For more information on StorageClass, see K8s Docs – StorageClass.

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: nvmesh-raid10
provisioner: nvmesh-csi.excelero.com
allowVolumeExpansion: true
volumeBindingMode: Immediate
mountOptions:
  - debug
parameters:
  vpg: DEFAULT_RAID_10_VPG

Provisioner

The provisioner field determines which storage backend driver / plugin will be used for provisioning the volume.
To create an NVMesh volume, this field must be set to: nvmesh-csi.excelero.com

Allow Volume Expansion (allowVolumeExpansion)

The field allowVolumeExpansion controls whether the volume should be expandable or not.
For more info, see K8s Docs – Allow Volume Expansion.

Volume Binding Mode (volumeBindingMode)

The volumeBindingMode field controls volume provisioning timing. The following values are accepted:

• Immediate: This is the default if omitted. If this value is set, dynamic provisioning occurs once the PersistentVolumeClaim is created.
• WaitForFirstConsumer: If this value is set, volume provisioning will be delayed until a Pod using the PersistentVolumeClaim is created.

For more info on volumeBindingMode, see K8s Docs – VolumeBindingMode

Mount Options (mountOptions)

The mountOptions field enables setting the options passed to the mount command (mount -o <options>) and a special key allows to set the mount permissions.

To set the mount permissions, for example to 777, use:

mountOptions:
  - nvmesh:permissions=777

*Mount options are not validated on either the class or PV. If a mount option is invalid, the PV mount fails.

Parameters

The parameters field is a structure used to define NVMesh specific parameters. The following parameters are accepted:

If raidLevel is defined, the following parameters are accepted according to the selected raidLevel:

• If raidLevel is raid0 or raid10
  • stripeSize (integer, optional) – number in blocks of 4k, i.e. stripeSize:32 = 128k, optional, defaults to 32.
  • stripeWidth (integer, optional) – number of disks to use, defaults to 2.

• If raidLevel is ec
  • dataBlocks (integer, optional) – number of disks to use, defaults to 8.
  • parityBlocks (integer, optional) – number of disks to use, defaults to 2.
  • protectionLevel (string, optional) – protection level to use, allowed values are Full Separation, Minimal Separation, Ignore Separation defaults to Full Separation.

*All integer values must be wrapped with quotes for Kubernetes to accept the yaml. i.e stripeWidth: "2".

*For more info on the specific fields, their purpose and allowed value range, see the NVMeshSDK Documentation. To open NVMeshSDK documentation, go to your NVMesh Management Server and on the top right corner click Docs > SDK.