When connecting a device like a disk drive to a controller like a SCSI controller or a USB controller, the maximum bandwidth that can be achieved by the device will be limited by:

whether the device is a block or character device

the bandwidth of the bus that the controller provides to the connecting device

whether the device has a major device code value above $100$

the amount of time that the controller$$s interrupt routine takes to run

the percent CPU utilization on the given system