This is unreleased documentation for SUSE® Storage 1.10.0 (Dev).

UBLK Frontend Support

Starting with v1.9.0, SUSE Storage supports the UBLK front-end for V2 Data Engine Volumes. This feature exposes V2 Data Engine volumes as a block device using the UBLK SPDK framework. In certain high-specification environments (for example, machines with fast SSDs capable of millions of IOPS and equipped with 32 CPU cores), the UBLK front-end might offer better performance compared to the default NVMe-oF front-end for V2 Data Engine volumes. For performance comparisons, see the SUSE Storage Performance Investigation wiki page. However, the UBLK front-end is less mature than the default NVMe-oF front-end (see Known Limitations). The UBLK front-end also has additional restrictions, as detailed below.

Prerequisites

  1. The kernel version on nodes must be v6.0 or later. The UBLK kernel driver is available only from kernel v6.0 onwards.

  2. The kernel module ublk_drv must be loaded on each node where UBLK volumes are to be attached. For testing, you can load it manually on each relevant node using the command:

    modprobe ublk_drv

How to use

When creating a V2 volume from the UI

Select UBLK as the volume front-end during volume creation.

When creating a V2 volume from a manifest

  1. Create a StorageClass that specifies the UBLK front-end. For example:

    kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: my-ublk-frontend-storageclass
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
parameters:
  numberOfReplicas: "1"
  staleReplicaTimeout: "2880"
  fsType: "ext4"
  dataEngine: "v2"
  frontend: "ublk"

  2. Create a PersistentVolumeClaim (PVC) that references the StorageClass created in the previous step. For example:

    apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-ublk-frontend-pvc
  namespace: default
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: my-ublk-frontend-storageclass
  resources:
    requests:
      storage: 1Gi

  3. SUSE Storage automatically provisions a V2 volume using the UBLK front-end based on the PVC and StorageClass definitions.

Known Limitations

When an instance-manager pod crashes, it might leave orphaned UBLK devices on the node. Currently, removing these orphaned devices manually can be difficult and might sometimes require a node reboot. We are investigating this issue further in GitHub Issue #10738.

Reference

Original GitHub issue for UBLK front-end support: GitHub Issue #9456.