Chapter 9. Creating Persistent Volumes

OpenShift Container Platform clusters can be provisioned with persistent storage using GlusterFS.

Persistent volumes (PVs) and persistent volume claims (PVCs) can share volumes across a single project. While the GlusterFS-specific information contained in a PV definition could also be defined directly in a pod definition, doing so does not create the volume as a distinct cluster resource, making the volume more susceptible to conflicts.

Binding PVs by Labels and Selectors

Labels are an OpenShift Container Platform feature that support user-defined tags (key-value pairs) as part of an object’s specification. Their primary purpose is to enable the arbitrary grouping of objects by defining identical labels among them. These labels can then be targeted by selectors to match all objects with specified label values. It is this functionality we will take advantage of to enable our PVC to bind to our PV.

You can use labels to identify common attributes or characteristics shared among volumes. For example, you can define the gluster volume to have a custom attribute (key) named storage-tier with a value of gold assigned. A claim will be able to select a PV with storage-tier=gold to match this PV.

More details for provisioning volumes in file based storage is provided in Section 9.1, “File Storage”. Similarly, further details for provisioning volumes in block based storage is provided in Section 9.2, “Block Storage”.

9.1. File Storage

File storage, also called file-level or file-based storage, stores data in a hierarchical structure. The data is saved in files and folders, and presented to both the system storing it and the system retrieving it in the same format. You can provision volumes either statically or dynamically for file based storage.

9.1.1. Static Provisioning of Volumes

To enable persistent volume support in OpenShift and Kubernetes, few endpoints and a service must be created:

The sample glusterfs endpoint file (sample-gluster-endpoints.yaml) and the sample glusterfs service file (sample-gluster-service.yaml) are available at /usr/share/heketi/templates/ directory.

Note

Ensure to copy the sample glusterfs endpoint file / glusterfs service file to a location of your choice and then edit the copied file. For example:

# cp /usr/share/heketi/templates/sample-gluster-endpoints.yaml /<path>/gluster-endpoints.yaml

To specify the endpoints you want to create, update the copied sample-gluster-endpoints.yaml file with the endpoints to be created based on the environment. Each Red Hat Gluster Storage trusted storage pool requires its own endpoint with the IP of the nodes in the trusted storage pool.
```
# cat sample-gluster-endpoints.yaml
apiVersion: v1
kind: Endpoints
metadata:
  name: glusterfs-cluster
subsets:
  - addresses:
      - ip: 192.168.10.100
    ports:
      - port: 1
  - addresses:
      - ip: 192.168.10.101
    ports:
      - port: 1
  - addresses:
      - ip: 192.168.10.102
    ports:
      - port: 1
```
name: is the name of the endpoint
ip: is the ip address of the Red Hat Gluster Storage nodes.

Execute the following command to create the endpoints:

# oc create -f <name_of_endpoint_file>

For example:

# oc create -f sample-gluster-endpoints.yaml
endpoints "glusterfs-cluster" created

To verify that the endpoints are created, execute the following command:

# oc get endpoints

For example:

# oc get endpoints
NAME                       ENDPOINTS                                                     AGE
storage-project-router     192.168.121.233:80,192.168.121.233:443,192.168.121.233:1936   2d
glusterfs-cluster          192.168.121.168:1,192.168.121.172:1,192.168.121.233:1         3s
heketi                     10.1.1.3:8080                                                 2m
heketi-storage-endpoints   192.168.121.168:1,192.168.121.172:1,192.168.121.233:1         3m

Execute the following command to create a gluster service:

# oc create -f <name_of_service_file>

For example:

# oc create -f sample-gluster-service.yaml
service "glusterfs-cluster" created

# cat sample-gluster-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: glusterfs-cluster
spec:
  ports:
    - port: 1

To verify that the service is created, execute the following command:

# oc get service

For example:

# oc get service
NAME                       CLUSTER-IP      EXTERNAL-IP   PORT(S)                   AGE
storage-project-router     172.30.94.109   <none>        80/TCP,443/TCP,1936/TCP   2d
glusterfs-cluster          172.30.212.6    <none>        1/TCP                     5s
heketi                     172.30.175.7    <none>        8080/TCP                  2m
heketi-storage-endpoints   172.30.18.24    <none>        1/TCP                     3m

Note

The endpoints and the services must be created for each project that requires a persistent storage.

Create a 100G persistent volume with Replica 3 from GlusterFS and output a persistent volume specification describing this volume to the file pv001.json:
```
$ heketi-cli volume create --size=100 --persistent-volume-file=pv001.json
```
```
cat pv001.json 
{
  "kind": "PersistentVolume",
  "apiVersion": "v1",
  "metadata": {
    "name": "glusterfs-f8c612ee",
    "creationTimestamp": null
  },
  "spec": {
    "capacity": {
      "storage": "100Gi"
    },
    "glusterfs": {
      "endpoints": "TYPE ENDPOINT HERE",
      "path": "vol_f8c612eea57556197511f6b8c54b6070"
    },
    "accessModes": [
      "ReadWriteMany"
    ],
    "persistentVolumeReclaimPolicy": "Retain"
  },
  "status": {}
```
Important
You must manually add the Labels information to the .json file.
Following is the example YAML file for reference:
```
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-storage-project-glusterfs1
  labels:
    storage-tier: gold
spec:
  capacity:
    storage: 12Gi
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  glusterfs:
    endpoints: TYPE END POINTS NAME HERE,
    path: vol_e6b77204ff54c779c042f570a71b1407
```
name: The name of the volume.
storage: The amount of storage allocated to this volume
glusterfs: The volume type being used, in this case the glusterfs plug-in
endpoints: The endpoints name that defines the trusted storage pool created
path: The Red Hat Gluster Storage volume that will be accessed from the Trusted Storage Pool.
accessModes: accessModes are used as labels to match a PV and a PVC. They currently do not define any form of access control.
lables: Use labels to identify common attributes or characteristics shared among volumes. In this case, we have defined the gluster volume to have a custom attribute (key) named storage-tier with a value of gold assigned. A claim will be able to select a PV with storage-tier=gold to match this PV.
Note
- heketi-cli also accepts the endpoint name on the command line (--persistent-volume-endpoint=”TYPE ENDPOINT HERE”). This can then be piped to oc create -f - to create the persistent volume immediately.
- If there are multiple Red Hat Gluster Storage trusted storage pools in your environment, you can check on which trusted storage pool the volume is created using the heketi-cli volume list command. This command lists the cluster name. You can then update the endpoint information in the pv001.json file accordingly.
- When creating a Heketi volume with only two nodes with the replica count set to the default value of three (replica 3), an error "No space" is displayed by Heketi as there is no space to create a replica set of three disks on three different nodes.
- If all the heketi-cli write operations (ex: volume create, cluster create..etc) fails and the read operations ( ex: topology info, volume info ..etc) are successful, then the possibility is that the gluster volume is operating in read-only mode.

Edit the pv001.json file and enter the name of the endpoint in the endpoint's section:

cat pv001.json
{
  "kind": "PersistentVolume",
  "apiVersion": "v1",
  "metadata": {
    "name": "glusterfs-f8c612ee",
    "creationTimestamp": null,
    "labels": {
      "storage-tier": "gold"
    }
  },
  "spec": {
    "capacity": {
      "storage": "12Gi"
    },
    "glusterfs": {
      "endpoints": "glusterfs-cluster",
      "path": "vol_f8c612eea57556197511f6b8c54b6070"
    },
    "accessModes": [
      "ReadWriteMany"
    ],
    "persistentVolumeReclaimPolicy": "Retain"
  },
  "status": {}
}

Create a persistent volume by executing the following command:

# oc create -f pv001.json

For example:

# oc create -f pv001.json
persistentvolume "glusterfs-4fc22ff9" created

To verify that the persistent volume is created, execute the following command:

# oc get pv

For example:

# oc get pv

NAME                 CAPACITY   ACCESSMODES   STATUS      CLAIM     REASON    AGE
glusterfs-4fc22ff9   100Gi      RWX           Available                       4s

Create a persistent volume claim file. For example:

# cat pvc.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: glusterfs-claim
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 100Gi
    selector:
      matchLabels:
        storage-tier: gold

Bind the persistent volume to the persistent volume claim by executing the following command:
```
# oc create -f pvc.yaml
```
For example:
```
# oc create -f pvc.yaml
persistentvolumeclaim"glusterfs-claim" created
```

To verify that the persistent volume and the persistent volume claim is bound, execute the following commands:

# oc get pv
# oc get pvc

For example:

# oc get pv

NAME                 CAPACITY   ACCESSMODES   STATUS    CLAIM                  REASON    AGE
glusterfs-4fc22ff9   100Gi      RWX           Bound     storage-project/glusterfs-claim             1m

# oc get pvc

NAME              STATUS    VOLUME               CAPACITY   ACCESSMODES   AGE
glusterfs-claim   Bound     glusterfs-4fc22ff9   100Gi      RWX           11s

The claim can now be used in the application:

For example:

# cat app.yaml

apiVersion: v1
kind: Pod
metadata:
  name: busybox
spec:
  containers:
    - image: busybox
      command:
        - sleep
        - "3600"
      name: busybox
      volumeMounts:
        - mountPath: /usr/share/busybox
          name: mypvc
  volumes:
    - name: mypvc
      persistentVolumeClaim:
        claimName: glusterfs-claim

# oc create -f app.yaml
pod "busybox" created

For more information about using the glusterfs claim in the application see, https://access.redhat.com/documentation/en/openshift-container-platform/3.6/single/installation-and-configuration/#install-config-storage-examples-gluster-example.

To verify that the pod is created, execute the following command:
```
# oc get pods
```

To verify that the persistent volume is mounted inside the container, execute the following command:

# oc rsh busybox

/ $ df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/mapper/docker-253:0-1310998-81732b5fd87c197f627a24bcd2777f12eec4ee937cc2660656908b2fa6359129
                      100.0G     34.1M     99.9G   0% /
tmpfs                     1.5G         0      1.5G   0% /dev
tmpfs                     1.5G         0      1.5G   0% /sys/fs/cgroup
192.168.121.168:vol_4fc22ff934e531dec3830cfbcad1eeae
                       99.9G     66.1M     99.9G   0% /usr/share/busybox
tmpfs                     1.5G         0      1.5G   0% /run/secrets
/dev/mapper/vg_vagrant-lv_root
                       37.7G      3.8G     32.0G  11% /dev/termination-log
tmpfs                     1.5G     12.0K      1.5G   0% /var/run/secretgit s/kubernetes.io/serviceaccount

Note

If you encounter a permission denied error on the mount point, then refer to section Gluster Volume Security at: https://access.redhat.com/documentation/en/openshift-container-platform/3.6/single/installation-and-configuration/#gluster-volume-security.

9.1.2. Dynamic Provisioning of Volumes

Dynamic provisioning enables provisioning of Red Hat Gluster Storage volume to a running application container without having to pre-create the volume. The volume will be created dynamically as the claim request comes in, and a volume of exactly the same size will be provisioned to the application containers.

Note

Dynamically provisioned Volumes are supported from Container-Native Storage 3.4. If you have any statically provisioned volumes and require more information about managing it, then refer Section 9.1.1, “Static Provisioning of Volumes”

9.1.2.1. Configuring Dynamic Provisioning of Volumes

To configure dynamic provisioning of volumes, the administrator must define StorageClass objects that describe named "classes" of storage offered in a cluster. After creating a Storage Class, a secret for heketi authentication must be created before proceeding with the creation of persistent volume claim.

9.1.2.1.1. Registering a Storage Class

When configuring a StorageClass object for persistent volume provisioning, the administrator must describe the type of provisioner to use and the parameters that will be used by the provisioner when it provisions a PersistentVolume belonging to the class.

To create a storage class execute the following command:
```
# cat glusterfs-storageclass.yaml


apiVersion: storage.k8s.io/v1beta1
kind: StorageClass
metadata:
  name: gluster-container
provisioner: kubernetes.io/glusterfs
parameters:
  resturl: "http://heketi-storage-project.cloudapps.mystorage.com"
  restuser: "admin"
  volumetype: "replicate:3"
  clusterid: "630372ccdc720a92c681fb928f27b53f,796e6db1981f369ea0340913eeea4c9a"
  secretNamespace: "default"
  secretName: "heketi-secret"
```
where,
resturl: Gluster REST service/Heketi service url which provision gluster volumes on demand. The general format must be IPaddress:Port and this is a mandatory parameter for GlusterFS dynamic provisioner. If Heketi service is exposed as a routable service in openshift/kubernetes setup, this can have a format similar to http://heketi-storage-project.cloudapps.mystorage.com where the fqdn is a resolvable heketi service url.
restuser : Gluster REST service/Heketi user who has access to create volumes in the trusted storage pool
volumetype: It specifies the volume type that is being used.
Note
Distributed-Three-way replication is the only supported volume type.
clusterid: It is the ID of the cluster which will be used by Heketi when provisioning the volume. It can also be a list of comma separated cluster IDs. This is an optional parameter.
Note
To get the cluster ID, execute the following command:
```
# heketi-cli cluster list
```
secretNamespace + secretName: Identification of Secret instance that contains the user password that is used when communicating with the Gluster REST service. These parameters are optional. Empty password will be used when both secretNamespace and secretName are omitted.
Note
When the persistent volumes are dynamically provisioned, the Gluster plugin automatically creates an endpoint and a headless service in the name gluster-dynamic-<claimname>. This dynamic endpoint and service will be deleted automatically when the persistent volume claim is deleted.

To register the storage class to Openshift, execute the following command:

# oc create -f glusterfs-storageclass.yaml
storageclass "gluster-container" created

To get the details of the storage class, execute the following command:

# oc describe storageclass gluster-container
                               
Name: gluster-container
IsDefaultClass: No
Annotations: <none>
Provisioner: kubernetes.io/glusterfs
Parameters: resturl=http://heketi-storage-project.cloudapps.mystorage.com,restuser=admin,secretName=heketi-secret,secretNamespace=default
No events.

9.1.2.1.2. Creating Secret for Heketi Authentication

To create a secret for Heketi authentication, execute the following commands:

Note

If the admin-key value (secret to access heketi to get the volume details) was not set during the deployment of Container-Native Storage, then the following steps can be omitted.

Create an encoded value for the password by executing the following command:
```
# echo -n "<key>" | base64
```
where “key” is the value for "admin-key" that was created while deploying Container-Native Storage
For example:
```
# echo -n "mypassword" | base64
bXlwYXNzd29yZA==
```

Create a secret file. A sample secret file is provided below:

# cat glusterfs-secret.yaml
                               
apiVersion: v1
kind: Secret
metadata:
  name: heketi-secret
  namespace: default
data:
  # base64 encoded password. E.g.: echo -n "mypassword" | base64
  key: bXlwYXNzd29yZA==
type: kubernetes.io/glusterfs

Register the secret on Openshift by executing the following command:
```
# oc create -f glusterfs-secret.yaml
secret "heketi-secret" created
```

9.1.2.1.3. Creating a Persistent Volume Claim

To create a persistent volume claim execute the following commands:

Create a Persistent Volume Claim file. A sample persistent volume claim is provided below:

# cat glusterfs-pvc-claim1.yaml
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: claim1
  annotations:
    volume.beta.kubernetes.io/storage-class: gluster-container
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 4Gi

# oc create -f glusterfs-pvc-claim1.yaml
persistentvolumeclaim "claim1" created

To get the details of the claim, execute the following command:

# oc describe pvc <claim_name>

For example:

# oc describe pvc claim1
                               
Name: claim1
Namespace: default
StorageClass: gluster-container
Status: Bound
Volume: pvc-54b88668-9da6-11e6-965e-54ee7551fd0c
Labels: <none>
Capacity: 4Gi
Access Modes: RWO
No events.

9.1.2.1.4. Verifying Claim Creation

To verify if the claim is created, execute the following commands:

To get the details of the persistent volume claim and persistent volume, execute the following command:

# oc get pv,pvc

NAME                                          CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS     CLAIM                    REASON    AGE
pv/pvc-962aa6d1-bddb-11e6-be23-5254009fc65b   4Gi        RWO           Delete          Bound      storage-project/claim1             3m

NAME         STATUS    VOLUME                                     CAPACITY   ACCESSMODES   AGE
pvc/claim1   Bound     pvc-962aa6d1-bddb-11e6-be23-5254009fc65b   4Gi        RWO           4m

To validate if the endpoint and the services are created as part of claim creation, execute the following command:

# oc get endpoints,service

NAME                          ENDPOINTS                                            AGE
ep/storage-project-router     192.168.68.3:443,192.168.68.3:1936,192.168.68.3:80   28d
ep/gluster-dynamic-claim1     192.168.68.2:1,192.168.68.3:1,192.168.68.4:1         5m
ep/heketi                     10.130.0.21:8080                                     21d
ep/heketi-storage-endpoints   192.168.68.2:1,192.168.68.3:1,192.168.68.4:1         25d

NAME                           CLUSTER-IP       EXTERNAL-IP   PORT(S)                   AGE
svc/storage-project-router     172.30.166.64    <none>        80/TCP,443/TCP,1936/TCP   28d
svc/gluster-dynamic-claim1     172.30.52.17     <none>        1/TCP                     5m
svc/heketi                     172.30.129.113   <none>        8080/TCP                  21d
svc/heketi-storage-endpoints   172.30.133.212   <none>        1/TCP                     25d

9.1.2.1.5. Using the Claim in a Pod

Execute the following steps to use the claim in a pod.

To use the claim in the application, for example

# cat app.yaml

apiVersion: v1
kind: Pod
metadata:
  name: busybox
spec:
  containers:
    - image: busybox
      command:
        - sleep
        - "3600"
      name: busybox
      volumeMounts:
        - mountPath: /usr/share/busybox
          name: mypvc
  volumes:
    - name: mypvc
      persistentVolumeClaim:
        claimName: claim1

# oc create -f app.yaml
pod "busybox" created

To verify that the pod is created, execute the following command:

# oc get pods

NAME                                READY     STATUS         RESTARTS   AGE
storage-project-router-1-at7tf      1/1       Running        0          13d
busybox                             1/1       Running        0          8s
glusterfs-dc-192.168.68.2-1-hu28h   1/1       Running        0          7d
glusterfs-dc-192.168.68.3-1-ytnlg   1/1       Running        0          7d
glusterfs-dc-192.168.68.4-1-juqcq   1/1       Running        0          13d
heketi-1-9r47c                      1/1       Running        0          13d

To verify that the persistent volume is mounted inside the container, execute the following command:

# oc rsh busybox

/ $ df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/mapper/docker-253:0-666733-38050a1d2cdb41dc00d60f25a7a295f6e89d4c529302fb2b93d8faa5a3205fb9
                         10.0G     33.8M      9.9G   0% /
tmpfs                    23.5G         0     23.5G   0% /dev
tmpfs                    23.5G         0     23.5G   0% /sys/fs/cgroup
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /run/secrets
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /dev/termination-log
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /etc/resolv.conf
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /etc/hostname
/dev/mapper/rhgs-root
                         17.5G      3.6G     13.8G  21% /etc/hosts
shm                      64.0M         0     64.0M   0% /dev/shm
192.168.68.2:vol_5b05cf2e5404afe614f8afa698792bae
                          4.0G     32.6M      4.0G   1% /usr/share/busybox
tmpfs                    23.5G     16.0K     23.5G   0% /var/run/secrets/kubernetes.io/serviceaccount
tmpfs                    23.5G         0     23.5G   0% /proc/kcore
tmpfs                    23.5G         0     23.5G   0% /proc/timer_stats

9.1.2.1.6. Deleting a Persistent Volume Claim

To delete a claim, execute the following command:

# oc delete pvc <claim-name>

For example:

# oc delete pvc claim1
persistentvolumeclaim "claim1" deleted

To verify if the claim is deleted, execute the following command:
```
# oc get pvc <claim-name>
```
For example:
```
# oc get pvc claim1
No resources found.
```
When the user deletes a persistent volume claim that is bound to a persistent volume created by dynamic provisioning, apart from deleting the persistent volume claim, Kubernetes will also delete the persistent volume, endpoints, service, and the actual volume. Execute the following commands if this has to be verified:
- To verify if the persistent volume is deleted, execute the following command:
```
# oc get pv <pv-name>
```
  For example:
```
# oc get pv pvc-962aa6d1-bddb-11e6-be23-5254009fc65b 
No resources found.
```
- To verify if the endpoints are deleted, execute the following command:
```
# oc get endpoints <endpointname>
```
  For example:
```
# oc get endpoints gluster-dynamic-claim1
No resources found.
```
- To verify if the service is deleted, execute the following command:
```
# oc get service <servicename>
```
  For example:
```
# oc get service gluster-dynamic-claim1 
No resources found.
```

9.1.3. Volume Security

Volumes come with a UID/GID of 0 (root). For an application pod to write to the volume, it should also have a UID/GID of 0 (root). With the volume security feature the administrator can now create a volume with a unique GID and the application pod can write to the volume using this unique GID

Volume security for statically provisioned volumes

To create a statically provisioned volume with a GID, execute the following command:

$ heketi-cli volume create --size=100 --persistent-volume-file=pv001.json --gid=590

In the above command, a 100G persistent volume with a GID of 590 is created and the output of the persistent volume specification describing this volume is added to the pv001.json file.

For more information about accessing the volume using this GID, refer https://access.redhat.com/documentation/en/openshift-container-platform/3.6/single/installation-and-configuration/#install-config-storage-examples-gluster-example.

Volume security for dynamically provisioned volumes

Two new parameters, gidMin and gidMax, are introduced with dynamic provisioner. These values allows the administrator to configure the GID range for the volume in the storage class. To set up the GID values and provide volume security for dynamically provisioned volumes, execute the following commands:

Create a storage class file with the GID values. For example:

# cat glusterfs-storageclass.yaml

apiVersion: storage.k8s.io/v1beta1
kind: StorageClass
metadata:
  name:gluster-container
provisioner: kubernetes.io/glusterfs
parameters:
  resturl: "http://heketi-storage-project.cloudapps.mystorage.com"
  restuser: "admin"
  secretNamespace: "default"
  secretName: "heketi-secret"
  gidMin: "2000"
  gidMax: "4000"

Note

If the gidMin and gidMax value are not provided, then the dynamic provisioned volumes will have the GID between 2000 and 2147483647.

Create a persistent volume claim. For more information see, Section 9.1.2.1.3, “Creating a Persistent Volume Claim”
Use the claim in the pod. Ensure that this pod is non-privileged. For more information see, Section 9.1.2.1.5, “Using the Claim in a Pod”
To verify if the GID is within the range specified, execute the following command:
```
# oc rsh busybox
```
```
$ id
```
For example:
```
$ id
uid=1000060000 gid=0(root) groups=0(root),2001
```
where, 2001 in the above output is the allocated GID for the persistent volume, which is within the range specified in the storage class. You can write to this volume with the allocated GID.
Note
When the persistent volume claim is deleted, the GID of the persistent volume is released from the pool.

Chapter 9. Creating Persistent Volumes

9.1. File Storage

9.1.1. Static Provisioning of Volumes

9.1.2. Dynamic Provisioning of Volumes

9.1.2.1. Configuring Dynamic Provisioning of Volumes

9.1.2.1.1. Registering a Storage Class

9.1.2.1.2. Creating Secret for Heketi Authentication

9.1.2.1.3. Creating a Persistent Volume Claim

9.1.2.1.4. Verifying Claim Creation

9.1.2.1.5. Using the Claim in a Pod

9.1.2.1.6. Deleting a Persistent Volume Claim

9.1.3. Volume Security

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