I understand how
ionice can help you when you have multiple processes requesting access to the same disk resources, but how does it work when you have multiple disks?
For example, you have one
rsync operation moving data from Drive A -> Drive B, and another
rsync moving data from Drive C -> Drive D.
In theory, since they are not competing for resources,
ionice'ing one of these
rsync processes shouldn't change its throughput. Is this how it works, or will it still impact performance?
Additionally, is there some "upper limit" on total I/O one might experience on a linux system that is independent of drive speed? Like if you hooked up 100 SSD drives, at some point would the OS run into a bottleneck aside from drive speed?