The stack is XFS inside cryptsetup inside mdraid on top of losetup. The directory containing the losetup block files
could be `rclone mount`'d from the WebDAV server, but that would make the setup unavailable if I didn't have network access. So instead I chose to have the block files in a regular directory, and I make sure to `rclone sync` that directory to the WebDAV server when I make changes in the XFS layer. Manually syncing also lets me run `sync` and watch the `rclone sync` output, which gives me greater confidence that all the layers have synced successfully.
>Ahh OK, I think I see -- since the block files are synced in full, you are always swapping blocks and doing ~1MB of writing no matter what.
Right. Let's say I update two files in the XFS layer. Those writes eventually result in three blocks in the lowest layer being modified. So now the `rclone sync` will need to do a `PUT` request to replace those three blocks on the WebDAV server, which means it'll upload 3MB of data to the server.
