On Wed, Mar 3, 2021 at 5:49 AM Sebastian Knust <sknust@physik.uni-bielefeld.de> wrote:
Hi,
Assuming a cluster (currently octopus, might upgrade to pacific once released) serving only CephFS and that only to a handful of kernel and fuse-clients (no OpenStack, CSI or similar): Are there any side effects of not using the ceph-mgr volumes module abstractions [1], namely subvolumes and subvolume groups, that I have to consider?
The "volume" abstraction helps with creating the file system/MDS and may help with management in the future. No side-effects for not using either one.
I would still only mount subtrees of the whole (single) CephFS file system and have some clients which mount multiple disjunct subtrees. Quotas would only be set on the subtree level which I am mounting, likewise file layouts. Snapshots (via mkdir in .snap) would be used on the mounting level or one level above.
Background: I don't require the abstraction features per se. Some restrictions (e.g. subvolume group snapshots not being supported) seem to me to be caused only by the abstraction layer and not the underlying CephFS. For my specific use case I require snapshots on the subvolume group layer. It therefore seems better to just forego the abstraction as a whole and work on bare CephFS.
subvolumegroup snapshots will come back, probably in a minor release of Pacific. -- Patrick Donnelly, Ph.D. He / Him / His Principal Software Engineer Red Hat Sunnyvale, CA GPG: 19F28A586F808C2402351B93C3301A3E258DD79D