K
Q

How to identify the storage space left in a PVC?

9/9/2019

I have a pod with PVC request of 10Gi and is successfully bound to PV(both definition below)

I came across the accepted answer of similar question, which suggests to run kubectl -n <namespace> exec <pod-name> df Upon doing the same i got the following -

pavan@p1: kubectl exec mysql-deployment-95f7dd544-mmjv9 df
Filesystem     1K-blocks    Used Available Use% Mounted on
overlay         51572172 5797112  43640736  12% /
tmpfs              65536       0     65536   0% /dev
tmpfs            1021680       0   1021680   0% /sys/fs/cgroup
/dev/vda1       51572172 5797112  43640736  12% /etc/hosts
shm                65536       0     65536   0% /dev/shm
tmpfs            1021680      12   1021668   1% /run/secrets/kubernetes.io/serviceaccount
tmpfs            1021680       0   1021680   0% /proc/acpi
tmpfs            1021680       0   1021680   0% /sys/firmware
pavan@p1: kubectl exec mysql-deployment-95f7dd544-mmjv9 -- df -h
Filesystem      Size  Used Avail Use% Mounted on
overlay          50G  5.6G   42G  12% /
tmpfs            64M     0   64M   0% /dev
tmpfs           998M     0  998M   0% /sys/fs/cgroup
/dev/vda1        50G  5.6G   42G  12% /etc/hosts
shm              64M     0   64M   0% /dev/shm
tmpfs           998M   12K  998M   1% /run/secrets/kubernetes.io/serviceaccount
tmpfs           998M     0  998M   0% /proc/acpi
tmpfs           998M     0  998M   0% /sys/firmware

I coudn't quite understand the o/p, i reqested for 10Gi and i don't see any mount with 10gi total capacity?

PV definition :

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/mysql"

PVC definition:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi

Deployment definition:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mysql-deployment
spec:
  replicas: 1
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: mysql-pod
  template:
    metadata:
      labels:
        app: mysql-pod
    spec:
      containers:
      - name: mysql-container
        image: mysql:5.7
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim

P.s: Node has a capacity of 50G

EDIT 1:

PV describe:

pavan@p1: kubectl describe pv/mysql-pv-volume
Name:            mysql-pv-volume
Labels:          type=local
Annotations:     kubectl.kubernetes.io/last-applied-configuration:
                   {"apiVersion":"v1","kind":"PersistentVolume","metadata":{"annotations":{},"labels":{"type":"local"},"name":"mysql-pv-volume"},"spec":{"acc...
                 pv.kubernetes.io/bound-by-controller: yes
Finalizers:      [kubernetes.io/pv-protection]
StorageClass:    manual
Status:          Bound
Claim:           default/mysql-pv-claim
Reclaim Policy:  Retain
Access Modes:    RWO
VolumeMode:      Filesystem
Capacity:        10Gi
Node Affinity:   <none>
Message:         
Source:
    Type:          HostPath (bare host directory volume)
    Path:          /mnt/mysql
    HostPathType:  
Events:            <none>

PVC describe:

pavan@p1: kubectl describe pvc/mysql-pv-claim
Name:          mysql-pv-claim
Namespace:     default
StorageClass:  manual
Status:        Bound
Volume:        mysql-pv-volume
Labels:        <none>
Annotations:   kubectl.kubernetes.io/last-applied-configuration:
                 {"apiVersion":"v1","kind":"PersistentVolumeClaim","metadata":{"annotations":{},"name":"mysql-pv-claim","namespace":"default"},"spec":{"acc...
               pv.kubernetes.io/bind-completed: yes
               pv.kubernetes.io/bound-by-controller: yes
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      10Gi
Access Modes:  RWO
VolumeMode:    Filesystem
Mounted By:    mysql-deployment-95f7dd544-mmjv9
Events:        <none>

Pod describe:

pavan@p1: kubectl describe pod/mysql-deployment-95f7dd544-mmjv9
Name:           mysql-deployment-95f7dd544-mmjv9
Namespace:      default
Priority:       0
Node:           pay0k-k8-dev-bytq/10.130.219.196
Start Time:     Mon, 09 Sep 2019 18:14:17 +0800
Labels:         app=mysql-pod
                pod-template-hash=95f7dd544
Annotations:    <none>
Status:         Running
IP:             10.244.0.123
Controlled By:  ReplicaSet/mysql-deployment-95f7dd544
Containers:
  mysql-container:
    Container ID:   docker://83f4730892fd6908ef3dfae3b9125d25cb7467d24df89323c43d3ab136376147
    Image:          mysql:5.7
    Image ID:       docker-pullable://mysql@sha256:1a121f2e7590f949b9ede7809395f209dd9910e331e8372e6682ba4bebcc020b
    Port:           3306/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Mon, 09 Sep 2019 18:14:19 +0800
    Ready:          True
    Restart Count:  0
    Environment:
      MYSQL_DATABASE:       <set to the key 'mysql-database' of config map 'mysqldb'>          Optional: false
      MYSQL_ROOT_PASSWORD:  <set to the key 'mysql-root-password' in secret 'db-credentials'>  Optional: false
      MYSQL_USER:           <set to the key 'mysql-user' in secret 'db-credentials'>           Optional: false
      MYSQL_PASSWORD:       <set to the key 'mysql-password' in secret 'db-credentials'>       Optional: false
    Mounts:
      /var/lib/mysql from mysql-persistent-storage (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-gbpxc (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  mysql-persistent-storage:
    Type:       PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:  mysql-pv-claim
    ReadOnly:   false
  default-token-gbpxc:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-gbpxc
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From                        Message
  ----    ------     ----  ----                        -------
  Normal  Scheduled  41m   default-scheduler           Successfully assigned default/mysql-deployment-95f7dd544-mmjv9 to pay0k-k8-dev-bytq
  Normal  Pulled     41m   kubelet, pay0k-k8-dev-bytq  Container image "mysql:5.7" already present on machine
  Normal  Created    41m   kubelet, pay0k-k8-dev-bytq  Created container mysql-container
  Normal  Started    41m   kubelet, pay0k-k8-dev-bytq  Started container mysql-container
-- Pavan
digital-ocean
kubernetes

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1 Answer

9/9/2019

In your PV definition your specify hostPath, so your data is stored directly on worker - this is why you see 50GB and you are skipping this additional layer provided by cloud provider which create pv directly from pvc.

Keeping data directly on a node isn't good approach because node could be removed/replaced at any time.

You should use digital ocean pvs instead of you're manually defined, if you spin new pod on digital ocean's pv output from df should show 10GB.

-- FL3SH
Source: StackOverflow