11. Storage Management

11. Storage Management#

        flowchart LR
    Pod[Pod] -->|mount| PVC[PersistentVolumeClaim]
    PVC -->|bind| PV[PersistentVolume]
    PV -->|provision| Storage[(Storage Backend<br/>NFS / EBS / Ceph)]
    SC[StorageClass] -->|dynamic provision| PV
    PVC -->|request| SC

Volume Types#

Type

Lifecycle

Use Case

emptyDir

Pod lifetime

Temp files, cache, inter-container sharing

hostPath

Node lifetime

Node-level logs, Docker socket

configMap

ConfigMap lifetime

Configuration files

secret

Secret lifetime

Credentials, TLS certs

persistentVolumeClaim

PVC lifetime

Databases, stateful apps

nfs

External

Shared storage across pods

emptyDir#

apiVersion: v1
kind: Pod
metadata:
  name: shared-data
spec:
  containers:
    - name: writer
      image: busybox
      command: ['sh', '-c', 'echo "hello" > /data/message; sleep 3600']
      volumeMounts:
        - name: shared
          mountPath: /data
    - name: reader
      image: busybox
      command: ['sh', '-c', 'cat /data/message; sleep 3600']
      volumeMounts:
        - name: shared
          mountPath: /data
  volumes:
    - name: shared
      emptyDir: {}
      # emptyDir:
      #   medium: Memory    # tmpfs (RAM-backed)
      #   sizeLimit: 256Mi

PersistentVolume and PersistentVolumeClaim#

# PersistentVolume (admin creates)
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  nfs:
    server: 192.168.1.100
    path: /exports/data
---
# PersistentVolumeClaim (user requests)
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: myapp-data
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 5Gi
---
# Pod using PVC
apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
    - name: app
      image: myapp:1.0
      volumeMounts:
        - name: data
          mountPath: /app/data
  volumes:
    - name: data
      persistentVolumeClaim:
        claimName: myapp-data

Access Modes#

Mode

Abbreviation

Description

ReadWriteOnce

RWO

Single node read-write

ReadOnlyMany

ROX

Multiple nodes read-only

ReadWriteMany

RWX

Multiple nodes read-write

ReadWriteOncePod

RWOP

Single pod read-write (K8s 1.27+)

StorageClass (Dynamic Provisioning)#

# StorageClass for AWS EBS
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: fast-ssd
provisioner: ebs.csi.aws.com
parameters:
  type: gp3
  iops: "3000"
  throughput: "125"
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
---
# StorageClass for local storage
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-storage
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer
---
# PVC using StorageClass
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: db-data
spec:
  storageClassName: fast-ssd
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 50Gi

NFS Storage#

# NFS server setup (Ubuntu)
sudo apt-get install nfs-kernel-server
sudo mkdir -p /exports/data
echo "/exports/data *(rw,sync,no_subtree_check,no_root_squash)" | sudo tee -a /etc/exports
sudo exportfs -ra
sudo systemctl restart nfs-kernel-server

# NFS PV
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv
spec:
  capacity:
    storage: 100Gi
  accessModes:
    - ReadWriteMany
  nfs:
    server: nfs-server.example.com
    path: /exports/data

Volume Snapshots#

# VolumeSnapshot
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: db-snapshot
spec:
  volumeSnapshotClassName: csi-snapclass
  source:
    persistentVolumeClaimName: db-data
---
# Restore from snapshot
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: db-data-restored
spec:
  storageClassName: fast-ssd
  dataSource:
    name: db-snapshot
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 50Gi
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