No. Remote storage providers only allow full files to be uploaded to them. They do not allow random access or appending to the uploaded files. That's why the backup has to first be taken on your server, then uploaded to a remote storage provider such as Dropbox.
If space is a problem please let me know, I can give you instructions to work around that. Basically, we can split the backup to smaller archive files (e.g. 100MB ones or even smaller) and have them uploaded to Dropbox as soon as we're done with them. The amount of space you will need on your server at any given time will be at most 2.5 times that limit, i.e. for an 100MB limit you will need at most 250MB of free space on your server. This would allow you to backup a site that's taking up most of the space available on your server.
Nicholas K. Dionysopoulos
Lead Developer and Director
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