How to share storage between Kubernetes pods?

Question

I am evaluating Kubernetes as a platform for our new application. For now, it looks all very exciting! However, I’m running into a problem: I’m hosting my cluster on GCE an

Answer 1

I just achieve this with an application made with 3 containerized micro-services, I have one of this that is responsible to store and share files, so the application is storing files and retrieving them on a folder, this folder is passed via application property. There is a secured rest entry point that is allowing submission and retrieving of files (basically at every submission it is creating a unique id that is returned and can be used to scan the folder for a file). Passing this application from docker-compose to kubernetes I had your same problem : I need a global disk so I can have multiple replica of the container, so when the other micro-services will send a request to one of the replica, they will always be able to send any submitted file, not only the replica file managed at submission. I solved by creating a persistent volume, associated to an persistent volume claim, this volume claim is associated to a deployment (note: not a Statefulset, that it will create a disk for every pod), at this point you have to associate the mounted volume path with the container storing folder path.

So what is important is just the persistent volume claim name and the fact that PV has more available memory of PVC, and obviously the matching with the deployment with the right labels. Then in the deployment you can pass in the spec:

volumes:
      - name: store-folder
        persistentVolumeClaim:
          claimName: [pvc_name]

into the container settings:

volumeMounts:
        - name: store-folder
          mountPath: "/stored-files"

and in env. block:

containers:
....
      - env:
        - name: any-property-used-inside-the-application-for-saving-files
          value: /stored-files

So, from volume, you bind the pvc to the deployment, than from volume mounts, you bind the disk to a directory, than via environment variable you are able to pass the persistent disk directory. It is fundamental that your declare both PVC and PV, without PV it will work like any pods has its own folder.