agree that simply increasing the number of stripes does already improve backup duration.

one would think it has to be on separate disks, but it does not necessarily have to be. there seems to be a sweet spot for the number of backup stripes on the same disk before it saturates it somehow.

we have a 20TB DB and we do 8 stripes and that has been acceptable since 2012. adding backup stripes will definitely shorten your backup duration.