Uploads (up to 4 at a time by default) start when the upload is completed to go.
--asynchronous-concurrent-upload-limit (Integer): The number of concurrent
uploads allowed
When performing asynchronous uploads, the maximum number of concurrent
uploads allowed. Set to zero to disable the limit.
* default value: 4
Default Remote volume size (Options sreen) is 50 MB, so it may take awhile.
Initial backup will find everything needs uploading. Later ones just do changes.