NewPopulator returns a Populator object to update the PV cache.

NewVolumeCache creates a new PV cache object for storing PVs created by this provisioner.

AnnProvisionedBy is the external provisioner annotation in PV object.

DefaultFsType is the filesystem type to mount.

DefaultMountPoint is the mount point of raid device on the host under in knode.

LocalFilesystemEnv will contain the filesystm path when script is invoked.

The Populator uses an Informer to populate the VolumeCache.

VolumeCache keeps all the PersistentVolumes that have been created by this provisioner.