On the MediaAgent, You can review the log, CVD.log -> which will show pipeline speed, for rate on how fast Client writes to MediaAgent.
For Disk IOPS, this will not be reported in the logs, but in CVD you can also see the physical write speed in mb/s to target storage.
Note - the write speed if at application level, if you want more granular logging, would recommend using the following:
- Resource Monitor for Windows
- IOstat for Linux
Hopefully this helps