Question about persistent storage

[Tim-herbie]

Hello,

I discovered Opencloud a few days ago and have started exploring the application — it looks great so far, well done!

I'm planning to set up a high-availability (HA) Opencloud deployment on Kubernetes and have a few questions regarding persistent storage. I've successfully connected Opencloud to my S3 bucket and can confirm that uploaded files are correctly stored there. Given this, I'm unsure about the role of the data folder in Opencloud's persistent volume.

Could you clarify what kind of data is stored in the persistent data directory and why it´s still necessary?

Thanks in advance for your help and for the great work on Opencloud!

[micbar]

Thank you for testing openCloud!

I am not sure, if the current helm chart already supports more than one replica per service.

@butonic is the maintainer

S3 Storage

This is not the preferred storage for openCloud although it is possible. The best option is GPFS or CephFS because metadata and data are stored together which makes backup and restore very simple and also offers some other powerful features like fast metadata operation and IoPs and features like directly editing files on the storage bypassing openCloud.

S3 is basically not a filesystem, it is an object Store. It cannot store metadata like stable file identifier(objectIDs are changing for new versions) and share information. So we need a second storage for metadata, file tree and share information. This is done on the storageusers data volume via a decomposed filesystem. This brings additional complexity: for backup you need two synchronized data snapshots of S3 and the data volume. That can be tricky.

Uploads to S3 are very slow, so OpenCloud needs to temporarily store uploads on the data volume of the storage users pod.

[micbar]

HA Storage

To enable high availability in openCloud, you need a RWX storage for the data volume of the storageusers pod which needs to be always consistent. That can currently be achieved either by

1. NFS v4 with all caches disabled and support for extended file attributes
2. CephFS
3. GPFS

[Tim-herbie]

Really appreciate all the details and the way you explained everything!