It could actually be the content directory you are selecting. Is D:\ a mapped to a file share or a physical drive on the machine?
If it is a mapping it could be puking on that. See note under step 4.
Create a data store—ArcGIS Data Store (Windows) Installation Guide | ArcGIS Enterprise
You can set the file store backups to a file share, but the Data Stores have to be on the local machine(s). If you need high availability, it will require a second machine and set that up as the standby.
This is all assuming it is the content directory. If not, disregard at your leisure. 🙂