Is it possible to mount different disks onto different subdirectories in Kubernetes?

Question

I am thinking of creating a setup where every directory inside main directory is mounted onto a different disk.

So basically volume config would mean I have 3 different volumes attached to 3 different persistent storage disks:

  volumes:
        - name: demo-pdf
          persistentVolumeClaim:
            claimName: demo-pdf
        - name: demo-tsv
          persistentVolumeClaim:
            claimName: demo-tsv
        - name: demo-csv
          persistentVolumeClaim:
            claimName: demo-csv

And then for volume mounts:

  volumeMounts:
            - name: demo-pdf
              mountPath: "/code/p_data/pdf"
              subPath: pdf
            - name: demo-tsv
              mountPath: "/code/p_data/tsv"
              subPath: tsv
            - name: demo-csv
              mountPath: "/code/p_data/csv"
              subPath: csv

But the app would still treat everything in the main p_data folder as single storage accesible by the app.

Is this setup achievable in Kubernetes and are there any significant drawbacks to this?

Answer 1

As per the official documentation

A process in a container sees a filesystem view composed from the initial contents of the container image, plus volumes (if defined) mounted inside the container. The process sees a root filesystem that initially matches the contents of the container image. Any writes within that filesystem hierarchy, if allowed, affect what that process views when it performs a subsequent filesystem access.

Since you are trying to mount three different volumes you just need to use a normal volume mount and mount these volumes in the exact path, subPath is used when you are trying to use a single volume for multiple subdirectories.

Try removing the subPath in your manifest file as given below

volumeMounts: 
       - name: demo-pdf 
         mountPath: "/code/p_data/pdf" 
       - name: demo-tsv 
         mountPath: "/code/p_data/tsv" 
       - name: demo-csv 
         mountPath: "/code/p_data/csv"