This page explains how to add a persistent disk to your cluster using the ReadOnlyMany access mode. This mode allows multiple Pods on different nodes to mount the disk for reading.
For more information on this mode, refer to persistent volume access modes .
Requirements
- Your cluster must run GKE version 1.22 or later.
- Your cluster must use the Compute Engine persistent disk CSI driver .
Format and populate a source persistent disk
To use a persistent disk in read-only mode, you must populate a source persistent disk with data, then either clone the volume or use a volume snapshot to move the data into a new ReadOnlyMany PersistentVolume.
-
Create a PersistentVolume using an existing persistent disk or using dynamic provisioning .
-
Format the disk and populate it with data. To format the disk, reference the disk as a ReadWriteOnce PersistentVolume in a Pod. GKE automatically formats the underlying disk, and lets the Pod write data to the disk. When the Pod starts, make sure the Pod writes the data you want to the disk.
Create a ReadOnlyMany
PersistentVolume
You can create a ReadOnlyMany
PersistentVolume using one of the following
methods:
- A volume snapshot of a source PersistentVolume that you populate with data.
- A volume clone of a source PersistentVolume that you populate with data.
-
A pre-existing persistent disk that was already populated with data.
Volume snapshot
-
Save the following PersistentVolumeClaim manifest as
snapshot-pvc.yaml:kind : PersistentVolumeClaim apiVersion : v1 metadata : namespace : PVC_NAMESPACE name : PVC_NAME spec : dataSource : apiGroup : snapshot.storage.k8s.io kind : VolumeSnapshot name : SNAPSHOT_NAME accessModes : - ReadOnlyMany storageClassName : premium-rwo resources : requests : storage : STORAGE_SIZEReplace the following:
-
PVC_NAMESPACE: the namespace of the new PersistentVolumeClaim. -
PVC_NAME: the name of the new PersistentVolumeClaim. -
SNAPSHOT_NAME:the name of yourVolumeSnapshotobject. -
STORAGE_SIZE: the amount of storage to request. This must be the same as the amount requested in the source PersistentVolumeClaim.
-
-
Apply the manifest to your cluster:
kubectl apply -f snapshot-pvc.yaml
This creates a new PersistentVolumeClaim named PVC_NAME
in your cluster, which
GKE uses to dynamically provision a new PersistentVolume
that contains the data from the snapshot of the source persistent disk.
Volume cloning
Before using volume cloning, make sure to familiarize yourself with the limitations of this approach .
-
Save the following manifest as
cloning-pvc.yaml:kind : PersistentVolumeClaim apiVersion : v1 metadata : namespace : PVC_NAMESPACE name : PVC_NAME spec : dataSource : name : SOURCE_PVC kind : PersistentVolumeClaim accessModes : - ReadOnlyMany storageClassName : STORAGE_CLASS_NAME resources : requests : storage : STORAGE_SIZEReplace the following:
-
PVC_NAMESPACE: the namespace of the new PersistentVolumeClaim. -
PVC_NAME: the name of the new PersistentVolumeClaim. -
SOURCE_PVC: the name of the source PersistentVolumeClaim populated with data. -
STORAGE_CLASS_NAME: the storage class for the new PersistentVolumeClaim. This must be the same as the storage class of the source PersistentVolumeClaim. -
STORAGE_SIZE: the amount of storage for the new PersistentVolumeClaim. This must be the same amount requested by the source PersistentVolumeClaim.
-
-
Apply the manifest to your cluster:
kubectl apply -f cloning-pvc.yaml
This creates a PersistentVolumeClaim named PVC_NAME
that GKE
uses to create a new PersistentVolume in ReadOnlyMany mode with the data
in the source PersistentVolume.
For more detailed information about Volume Cloning, see Create clones of persistent volumes .
Pre-existing persistent disk
-
Save the following manifest as
preexisting-disk-pv-pvc.yaml:apiVersion : v1 kind : PersistentVolume metadata : name : PV_NAME spec : storageClassName : " STORAGE_CLASS_NAME " capacity : storage : DISK_SIZE accessModes : - ReadOnlyMany claimRef : namespace : PVC_NAMESPACE name : PVC_NAME csi : driver : pd.csi.storage.gke.io volumeHandle : DISK_ID fsType : FS_TYPE readOnly : true --- apiVersion : v1 kind : PersistentVolumeClaim metadata : namespace : PVC_NAMESPACE name : PVC_NAME spec : storageClassName : " STORAGE_CLASS_NAME " volumeName : PV_NAME accessModes : - ReadOnlyMany resources : requests : storage : DISK_SIZEReplace the following:
-
PV_NAME: the name of your new PersistentVolume. -
STORAGE_CLASS_NAME: the name of your new StorageClass. -
DISK_SIZE: the size of your pre-existing persistent disk. For example,500G. -
PVC_NAMESPACE: the namespace of the new PersistentVolumeClaim. -
PVC_NAME: the name of your new PersistentVolumeClaim. -
DISK_ID: the identifier of your pre-existing persistent disk. The format isprojects/{project_id}/zones/{zone_name}/disks/{disk_name}for Zonal persistent disks , orprojects/{project_id}/regions/{region_name}/disks/{disk_name}for Regional persistent disks . -
FS_TYPE: the filesystem type. You can leave this as the default (ext4), or usexfs. If your clusters use a Windows Server node pool, you must change this toNTFS.
-
-
Apply the manifest to your cluster:
kubectl apply -f preexisting-disk-pv-pvc.yaml
This creates a PersistentVolumeClaim named PVC_NAME
and a PersistentVolume named PV_NAME
in ReadOnlyMany mode.
For more detailed information about using a pre-existing persistent disk, see existing persistent disk .
Use the PersistentVolumeClaim in a Pod
You can now reference the new PersistentVolumeClaim in read-only mode in multiple Pods on multiple nodes at the same time. You cannot attach persistent disks in ReadWriteOnce mode to multiple nodes at the same time. For more information, refer to Deployments vs. StatefulSets .
In your Pod specification, you must specify readOnly: true
in the volumeMounts
section and the volumes
section, such as in the following
example:
apiVersion
:
apps/v1
kind
:
Deployment
metadata
:
name
:
multi-read
labels
:
app
:
web-server
spec
:
replicas
:
3
selector
:
matchLabels
:
app
:
web-server
template
:
metadata
:
labels
:
app
:
web-server
spec
:
containers
:
-
name
:
web-server
image
:
nginx
volumeMounts
:
-
mountPath
:
/test-mnt
name
:
my-volume
readOnly
:
true
volumes
:
-
name
:
my-volume
persistentVolumeClaim
:
claimName
:
PVC_NAME
readOnly
:
true
What's next
- Learn more about using pre-existing persistent disks as PersistentVolumes .
- Learn more about Compute Engine persistent disks .
