Need explanation on odd figures from Copy/Transfer rates

---------------
--Update--
---------------

So basically the issue (You can read in details bellow) was that on copying files one gets three different readings , Explorer report a figure between 35 ~ 70 MB/s , Task Manager Disk % Transfer Rate reports double the number & yet Disk % Utilization never exceeds 50~60% .

Thanks to @dalchina & @Samuria I was able to experiment with the issue a little more and here are my findings :

1 - Apparently on file Copy windows deal with Explorer as yet another program running with Normal priority assigning to it a Quota of Disk % Utilization (a Cap) where Explorer as a program do the Reading then hands it in a Queue like action to the System Process to do the Writing , so Explorer just report its part (the Reading speed in MB/s) and yet Disk % Transfer rate combines it along with the Writing done by the System as well :


2 - The reason of priority and capping was revealed to me as on conducting the same experiment with Robocopy (A fast folder copy command line tool suggested by Samuria) , when the system reached its Disk % Utilization peek (95~100%) the system starts becoming slightly unresponsive .

3 - Now on the other hand Robocopy command despite not running in any higher priority somehow trigger the System to assist it in Reading so the Cap limiting is off (i.e the System Read along with it at the exact capped speed) to render a full Disk % Utilization :


4 - There are few side effects to Robocopy other than System responsiveness and those are :
a - The documentation is Jerky
b - You can't monitor progress or have an estimate on when it's done
c - It uses an odd method of committing all files in last step
(i.e you wont be seeing a single file output until it is done copying/moving all)
d - It is designed for directory copy , no file copy support

5 - Microsoft made a GUI for Robocopy as it is essentially a command line tool which is difficult to find so I have included it in post attachments yet however it only ease up using it but wouldn't solve the no progress monitor or time estimate or pause or cancel problem etc .

Cheers


-----------------------
--Original Post--
-----------------------
Ok so basically I am trying to figure why would I get 3 different readings from windows from a file Copy/Move operation , first things first this is an internal SSHD trying to copy files to another internal SSHD both running on a Sata 3 interface .

Now the remark is I get a fluctuating rate between 70 ~ 35 MB/s reported on Copy/Transfer Dialogue and then exactly double the figure on Task Manager "Disk % Transfer Rate" and Yet less than 50% Cap to "Disk % Utilization" .



Now Maybe but not really sure I can assume that the "Disk % Transfer Rate" doubles figures to portray cumulative disk utilization of both disks . Now why is it still capped under 50% if the Sata interface can take it ? Defragmantation ? Can defragmentation cause a 50% cap ?

Which lead me to try it but this time to a USB 3 external HDD and here are the results :



Again the numbers are doubled in "Disk % Transfer Rate" and while the transfer rate is higher the "Disk % Utilization" is lower , so can anyone confirm why these numbers are all messed up like that ?

Hi, if you look at your Resource Monitor with activity on 1 physical disk only, you should be able to work out what means what:



There you can see read, write, and total.

Also see the disk transfer rate under the Performance tab.