User home directory storage

All users on all the hubs get a home directory with persistent storage. This is made available through a Network File System (NFS) that allows remote systems to access a storage resource over the network using a server-client model.

../_images/pilot-hubs-storage-layer.png

NFS Server setup

Each of the 2i2c clusters has a NFS server that is usually located at nfs-server-01. This is currently hand configured, so it might change in the future. This NFS Server has a persistent disk that’s independent from rest of the VM (it can be grown / snapshotted independently). This disk is mounted inside the NFS server at /export/home-01 (for the home directories of users) and is made available via NFS to be mounted by everything in the cluster, via /etc/exports:

/export/home-01 10.0.0.0/8(all_squash,anonuid=1000,anongid=1000,no_subtree_check,rw,sync)

Note

To SSH into the NFS server run:

gcloud compute ssh nfs-server-01 --zone=us-central1-b

NFS Client setup

For each hub, there needs to be a:

Hub directory

A directory is created under /export/home-01/homes for each hub. This the the base directory under which each hub has a directory (nfs.pv.baseShareName). This is done through a job that’s created for each deployment via helm hooks that will mount nfs.pv.baseShareName, and make sure the directory for the hub is present on the NFS server with appropriate permissions.

Note

The NFS share creator job will be created pre-deploy, run, and cleaned up before deployment proceeds. Ideally, this would only happen once per hub setup - but we don’t have a clear way to do that yet.

Hub user mount

For each hub, a PersistentVolumeClaim(PVC) and a PersistentVolume(PV) are created. This is the Kubernetes Volume that refers to the actual storage on the NFS server. The volume points to the hub directory created for the hub and user at /export/home-01/homes/<hub-name>/<username> (this name is dynamically determined as a combination of nfs.pv.baseShareName and the current release name). Z2jh then mounts the PVC on each user pod as a volume named home.

Parts of the home volume are mounted in different places for the users:

  • user home directories

    Z2jh will mount into /home/jovyan (the mount path) the contents of the path /exports/home-01/<hub-name>/<username> on the NFS storage server. Note that <username> is specified as a subPath - the subdirectory in the volume to mount at that given location.

  • shared directories

    • /home/jovyan/shared

      Mounted for all users, showing the contents of /exports/home-01/homes/<hub-name>/_shared. This mount is readOnly and users can’t write to it.

    • /home/jovyan/shared-readwrite

      Mounted just for admins, showing the contents of /exports/home-01/homes/<hub-name>/_shared. This volumeMount is NOT readonly, so admins can write to it.

      Note

      This feature comes from the custom KubeSpawner that the pilot hubs use, that allows providing extra configuration for admin users only.