Remove default for worker_root_disk in scs cluster stack

[Nils98Ar]

I think it is not possible to use local storage root disks for worker nodes at the moment.

If I use a diskful flavor and I do not define the worker_root_disk variable in my cluster object it creates a 25Gi volume and uses it as root disk.

cluster-stacks/providers/openstack/scs/cluster-class/templates/cluster-class.yaml

Line 74 in 5100655

default: 25

[garloff]

OK, so we have two possibilities to provide a set of defaults that work:

1. Default to a diskless worker_flavor e.g. SCS-2V-4 and a default worker_root_disk of e.g. 25. Then using a diskful flavor requires to change two settings. (@Nils98Ar - is it not possible to set worker_root_disk to 0?)
2. Default to a diskful worker_flavor e.g. SCS-2V-4-20s (not much other choices here if we want to stick to flavors that do exist everywhere in SCS Land) and don't set worker_root_disk. Then using diskless requires two changes.

Neither is perfect. If it's really impossible to unset worker_root_disk, then choice number 1 becomes bad ...

[Nils98Ar]

Currently the minimum is 1:

cluster-stacks/providers/openstack/scs/cluster-class/templates/cluster-class.yaml

Line 73 in 5100655

minimum: 1

Not sure if using worker_root_disk: 0 would unset it after removing the minimum in the schema.

[garloff]

In PR #238, we allow a minimum of 0 for both workerRootDisk and controlPlaneRootDisk which addresses this.

Changing the defaults for controlPlaneFlavor to SCS-2V-4-20s and controlPlaneRootDisk to 0 would have been a good idea, but we unfortunately overlooked this when crafting the scs2 ClusterStack release.
I would be careful to do such a change without a "major" release, as it could break existing clusters.
But allowing 0 achieves you what you want, see #238 (comment)

[garloff]

I consider this resolved, as we can not do any better:

• Changing the default to 0 is a breaking change (people that previously relied on a reasonable default would run into issues)
• We unfortunately failed to change the default to 0 when we did scs2
• But we allow for setting it to zero now (since openstack-scs2-1-33-v2 (k8s-v1.33.5) cluster stack release and it does what is wanted (not allocating a cinder root disk)

Please reopen if you disagree, @Nils98Ar (or anyone else involved).
Also, when we start dicussing scs3 (in case we have a set of breaking changes again), feel free to remind us to consider this change again.

[Nils98Ar]

That's okay for me. I'll make some adjustments to scs2 for us anyway and release it to our own OCI registry. Probably not until January.