File Read Bytes/sec is the overall rate at which bytes are read to satisfy file system read requests to all devices on the ...

File Read Bytes/sec is the overall rate at which bytes are read to satisfy  file system read requests to all devices on the computer, including reads from the file system cache.  It is measured in number of bytes per second.  This counter displays the difference between the values observed in the last two samples, divided by the duration of the sample interval.