I'm using a Western Digital NTFS formatted and a Samsung exFAT formatted USB drive together with my Raspberry Pi Model B+ and OMV.
With the WD drive everything works perfectly fine (read/write from my Windows 10 with SMB),
On my exFAT Samsung drive I've only read access.
Shared folder privileges (Menu: Access Rights Management/Shared Folders/Privileges) are set to read/write for all users and in the Menu "Services/SMB/CIFS/Shares" the read-only switches are NOT set. Both drives are mounted at the root (Relative Path = "/")
I know that formatting the Samsung T5 with ext4 or NTFS would presumably solve this problem. But then I would lose read/write access to the Samsung drive from my Windows and from my Mac (without adding additional drivers on these systems)
I guess this is a bug in the current version of OMV and it would be worth finding a solution or at least a workaround for this issue.