Use QuotaPath volumes - Container Service for Kubernetes

You can use the project quota feature of file systems on local disks, such as the Ext4 file system. The project quota feature allows you to control the disk quota at the directory level. You can also use the CSI plug-in to manage the lifecycle of QuotaPath volumes, such as division, quota limit, and mounting of QuotaPath volumes. This topic describes how to use QuotaPath volumes.

Prerequisites

The Container Storage Interface (CSI) plug-in for logical volumes (LVs) is deployed. For more information, see Step 2: Deploy CSI-Plugin and CSI-Provisioner.

Differences among QuotaPath volumes, hostPath volumes, and LVs

To enable pods to use the storage of nodes, you can use hostPath volumes, LVs, and QuotaPath volumes. However, each type of volume has the following limits:

hostPath volumes share a directory which can be divided into multiple subdirectories. The subdirectories share the space and I/O of the same disk.
Logical Volume Manager (LVM) virtualizes the disk and divides the disk into multiple volumes. Each volume has an independent storage quota.
The QuotaPath volume uses the quota feature of file systems. This feature allows you to divide the directory into multiple directories. Each directory has an independent storage quota.

Features

Lifecycle management of QuotaPath volumes: automatic creation, deletion, mounting, and unmounting.
Expansion of QuotaPath volumes.
Automatic operations and maintenance of root directories where QuotaPath volumes are mounted. This enables you to manage the local storage of nodes.
Storage usage monitoring for clusters that use QuotaPath volumes.

Precautions

QuotaPath volumes are not applicable to scenarios where the high availability of data must be guaranteed.
The features of automatic operations and maintenance of root directories and storage usage monitoring for clusters that use QuotaPath volumes are not supported in current versions.
If you run a pod as the root user in privileged mode, the project quota feature of file systems on local disks, such as the Ext4 file system, does not take effect.

Examples

When you use CSI-Provisioner to create persistent volumes (PVs), take note of the following limits:

You must specify the name of the rootPath in a StorageClass.
If you want to create a PV on a specified node, you must add the volume.kubernetes.io/selected-node: nodeName label to the related PVC.

Create a StorageClass.

Create a file named alicloud-local-quota.yaml and copy the following content to the file:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: alicloud-local-quota
parameters:
  volumeType: QuotaPath
  rootPath: /mnt/quota
provisioner: localplugin.csi.alibabacloud.com
reclaimPolicy: Delete
allowVolumeExpansion: true
volumeBindingMode: WaitForFirstConsumer


Parameter	Description
volumeType	The type of volume. The volume type is set to QuotaPath in this example.
rootPath	Specifies the name of the directory where the QuotaPath volume is mounted.

Run the following command to create a StorageClass:
```
kubectl create -f alicloud-local-quota.yaml
```

Create a persistent volume claim (PVC).
1. Create a file named csi-quota.yaml and copy the following content to the file:
  By default, the CSI plug-in uses /mnt/quotapath.namespacex.x as the root directory of QuotaPath volumes. All PVs are mounted to subdirectories in this root directory.
  
  You can add the following annotation to the PVC to define the parent directory of the QuotaPath volume: volume.kubernetes.io/selected-storage: /mnt/xxx.
```
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: csi-quota
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi
  storageClassName: alicloud-local-quota
```
2. Run the following command to create a PVC:
```
kubectl create -f csi-quota.yaml
```

Use the following template to create an application:

Create a file named web-quota.yaml file and copy the following content to the file:

apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web-quota
spec:
  selector:
    matchLabels:
      app: nginx
  serviceName: "nginx"
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        volumeMounts:
        - name: disk-ssd
          mountPath: /data
      volumes:
        - name: "disk-ssd"
          persistentVolumeClaim:
            claimName: csi-quota

Run the following commands to create an application:
```
kubectl create -f web-quota.yaml
```

Query the status of the application.

Run the following command to query the pod that runs the application:

kubectl get pod |grep quota

Expected output:

NAME          READY   STATUS    RESTARTS   AGE
web-quota-0   1/1     Running   0          16s

Run the following command to query PVC information:

kubectl get pvc

Expected output:

NAME        STATUS   VOLUME                CAPACITY   ACCESS MODES   STORAGECLASS           AGE
csi-quota   Bound    local-f4b129a5-****   2Gi        RWO            alicloud-local-quota   48s

Run the following command to query PV information:

kubectl get pv |grep quota

Expected output:

NAME                  CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM               STORAGECLASS           REASON   AGE
local-f4b129a5-****   2Gi        RWO            Delete           Bound    default/csi-quota   alicloud-local-quota            66s

Run the following command to query the storage information about the LV that is mounted to the /data directory of the pod:

kubectl exec -ti web-quota-0 sh
df |grep data

Expected output:

Filesystem  1K-blocks  Used Available Use% Mounted on
/dev/vdd    2097152       4   2097148   1% /data

Run the following command to query all directories in the /data directory:

ls /data

Expected output:

lost+found

Run the following command to create a directory named test in the /data directory:

touch /data/test
ls /data

Expected output:

lost+found test

Expand the QuotaPath volume.

Run the following command to query PVC information:

kubectl get pvc

Expected output:

NAME        STATUS   VOLUME                CAPACITY   ACCESS MODES   STORAGECLASS           AGE
csi-quota   Bound    local-f4b129a5-****   2Gi        RWO            alicloud-local-quota   42s

Run the following command to expand the PVC to 3 GiB:

kubectl patch pvc csi-quota -p '{"spec":{"resources":{"requests":{"storage":"3Gi"}}}}'

Expected output:

persistentvolumeclaim/csi-quota patched

Run the following command to query PVC information:

kubectl get pvc

Expected output:

NAME        STATUS   VOLUME                CAPACITY   ACCESS MODES   STORAGECLASS           AGE
csi-quota   Bound    local-f4b129a5-****   3Gi        RWO            alicloud-local-quota   4m30s

Run the following command to check whether the QuotaPath volume is expanded to 3 GiB:

kubectl exec -ti web-quota-0 sh
df |grep data

Expected output:

Filesystem  1K-blocks  Used Available Use% Mounted on
/dev/vdd    3145728       4   3145724   1% /data