Kubernetes - Storage

Docker Storage local file system

• /var/lib/docker
  • aufs
  • containers
  • image
  • volumes

Layered architecture

1. Image layers (Read Only)
   • base OS Layer
   • apt packages
   • pip packages
   • source code
   • update entrypoint with “flask” command
2. Container Layer (Read Write)
   • container layer

what if we want to persist these data we cloud add a persistent volume

docker volume create data_volume

• /var/lib/docker
  • aufs
  • containers
  • image
  • volumes
    • data_volume

1. volume mount

docker run -v data_volue:/var/lib/mysql mysql

1. bind mount

docker run -v /data/mysql:/var/lib/mysql mysql

docker run --mount type=bind,source=/data/mysql,target=/var/lib/mysql mysql

• Storage drivers
  • AUFS (default)
  • ZFS
  • BTRFS
  • Device Mapper
  • Overlay
  • Overlay2
• Volume drivers
  • local
  • Azure File Storage
  • Convoy
  • DigitalOcean Block Storage
  • Flocker
  • gce-docker
  • GlusterFS
  • NetApp
  • RexRay
  • Portworx
  • VMware vSphere Storage

Container Storage Interface (CSI)

in the past, k8s used docker only for container runtime

Container Storage Interface (CSI)

SHOULD call to provision/delete/place/decommission/make ….

Container Network Interface (CNI)

Volumes

Volume 을 붙여서 data를 permanently store

Volumes & Mounts

# local-volume-pod-definition.yaml

kind: Pod
apiVersion:
metadata:
spec:
  containers:
  - ...
    volumeMounts:
    - mountPath: /opt
      name: data-volume
  volumes:
    - name: data-volume
      hostPath:
        path: /data
        type: Directory

# pvc-pod-definition.yaml

kind: Pod
apiVersion:
metadata:
spec:
  containers:
  - ...
    volumeMounts:
    - mountPath: /opt
      name: data-volume
  volumes:
    - name: data-volume
      persistentVolumeClaim:
        claimName: pv-claim

# aws-ebs-volume-pod-definition.yaml

kind: Pod
apiVersion:
metadata:
spec:
  containers:
  - image:
    volumeMounts:
    - mountPath: /opt
      name: data-volume
  volumes:
    - name: data-volume
      awsElasticBlockStore:
        volumeID: <volume-id>
        fsType: ext4

Persistent Volumes

Pod can use Persistent Volumes(PV)

# pv-definition.yaml

kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv-log
spec:
  persistentVolumeReclaimPolicy: Retain
  accessModes:
    - ReadWriteMany
  capacity:
    storage: 100Mi
  hostPath:
    path: /pv/log

# pv-definition.yaml

kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv-vol1
spec:
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 1Gi
  awsElasticBlockStore:
    volumeID: <volume-id>
    fsType: ext4

Persistent Volume Claims

make the storage available to nodes

# pvc-definition.yaml

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: myclaim
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 500Mi

kubectl create -f pvc-definition.yaml
kubectl get pvc
kubectl delete pvc myclaim

1. persistentVolumeReclaimPolicy: Retain (default, remain until manually delete)
2. persistentVolumeReclaimPolicy: Delete (delete automatically)
3. persistentVolumeReclaimPolicy: Recycle (scrubbed to other claim)

Configure Apps on Persistent Volumes

Access Modes for Volumes

Kubernetes Storage Object

Storage Classes

1. Static Provisioning
   • last_modified_at
   • asdf
2. Dynamic Provisioning

# storage-class-definition.yaml

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: google-storage
provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-standard | pd-ssd
  replication-type: none | regional-pd
volumeBindingMode: WaitForFirstConsumer | Immediate

# pvc-definition.yaml

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: some-pvc
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: google-storage
  resources:
    requests:
      storage: 500Mi

.