I know about the options --checkers and --transfers but I need to run only one task at any time. This could be a --workers option to limit the number of disk workers (checkers and transfers combined) to run in parallel.
I am using an archiving disk (Seagate Archive HDD) to move my data around.
The disk can read with 200 MB/s as long as only a single operation is using the disk. As soon as 2 or more operations try to access data on the disk read thorughput drops to 20 MB/s.
Now I need to copy my data from the disk to gdrive, some of which is already there.
I start out with a single checker running at 200 MB/s but as soon as a transfer starts along with it my performance goes down a lot.
With a --workers option I could ensure that only either a checker or a transfer is running optimizing disk performance.
Others could better optimize disk and transfer throughput by tweaking --workers, --transfers and --checkers to their needs.