Yes, ext4... So onto Synology Drive... Just FYI... but any shared folders for which versioning is enabled will double their file storage use at the outset. For example, if you choose to version a 500GB shared folder, 1TB of space is required.... 500GB for the active files, and 500 GB for a baseline copy that versioning uses (not applicable to btrfs formatted volumes).
For Synology Drive Server... you can see versioning here:
Unless you have a specific need for Drive, perhaps uninstall Drive Server fully, including settings/backups/versions.
Then examine your drive contents.
Alternately, you can stop Synology Driver Server, SSH in to your NAS and examine folder sizes. If the @synologydrive folder is the issue, delete it (which will delete all backups/versions). After exiting SSH, check your drive utilization.
To clear the versions and also the associated Drive database storage: select the Team folder then click Versioning. You can either reduce the maximum versions (which will reduce DB storage) or just disable version control. Repeat for other Team folders.
Agree with Fredbert, but I would point out that when you reduce the number of versions saved, or otherwise change the versioning, it can take time (more than a few minutes...) to see the effects. You won't see an immediate reduction in disk space usage, you have to be patient.
OK, thanks all. I've got my storage space back to where it was before I installed Drive (that package has been disabled now).
Back to the original issue in the post: Why am I blocked out of my drive on the local network???
EDIT: A bit more investigation reveals that it was my desktop (192.168.1.20) on my local network that was permanently blocked. I deleted that IP address in the autoblock section but wonder why it was blocked in the first place?