Make minimum volume capacity configurable

[hotpheex]

I'm getting this error when requesting a volume <1Gi:
GRPC error: rpc error: code = InvalidArgument desc = Invalid input: required bytes is smaller than 1G

From what I can tell this is defaulting to a 1Gi minimum size if a custom range is not provided, but I cannot see a way for a user to configure the value. Is a 1Gi minimum volume size a limitation of Synology or is it possible to just add another flag to override it? Happy to raise a PR if its just a case of passing in a new value.

synology-csi/pkg/driver/controllerserver.go

Lines 46 to 48 in 53cefcb

	if capRange == nil {
	return 1 * utils.UNIT_GB, nil
	}

[chihyuwu]

hi @hotpheex,
Yes, the 1Gi minimum size is a limitation of Synology LUNs, as specified in the documentation.

In Synology DSM, the minimum size for a LUN is 1GB(Gi), and the minimum quota for a shared folder is 1MB(Mi).
In the current implementation of synology-csi, we have standardized the minimum volume size to 1GB.
Perhaps a better approach would be allowing file protocols, such as SMB and NFS, to set the size smaller than 1Gi (but at least 1Mi).

Certainly appreciate your raising a PR! The earlier suggestion is something you might consider. Thank you in advance for your contribution!