How to check disk utilization on Windows Server 2016?

Question

Windows Server

Initial:
Windows Server 2016 Standard
disks for the OS are assembled in RAID1, the raid, in turn, uses the ASROCK X79 EXTREME6 built-in motherboard chip, the SAMSUNG HD321KJ disks themselves.
In addition, the disks are encrypted with bitlocker It slows down
the operation of the OS and applications on it. It is executed mainly by loading RDP, DBMS (MSSQLSERVER, PosgtreSQL) 1C, libre.
The issue with the rest of the components is not close. The processor, RAM, network are not loaded and the stock is huge. But the disks also seem to be not loaded according to the following counters: average disk queue length, average disk read time, average disk write time, Page exchange / sec. However, taking into account the fact that these specific disk models have an "external data transfer rate" of 300Mb / s, I am inclined that the disks need to be changed. However, the authorities do not want to change them, an argument is needed. I don't know how to express it in numbers. There are only suspicions based on experience with this OS. As far as I know, there is no specific counter to check exactly this characteristic of the disk "external data transfer rate".
Yes, I understand that in general the chip on the motherboard is not needed at all, including your enemies, but you need a normal hardware RAID. Yes, I understand that the disks are, to put it mildly, poor even by the standards of a home user for such a type of load as the above. Unfortunately, I have not studied molecular administration and have not dug into such jungle in order to have some numerically expressed indicator that will unequivocally say that yes, it is necessary to change disks. The fucked-up boss imagined himself an admin, because ten years ago he pressed 5 buttons and now, in addition to working as an admin, I still have to work as a legend buster. At a minimum, I was not able to persuade not to use RAID on the motherboard, although in this example I understand that there is an elementary risk of losing data or malfunctioning RAID in the event of a power failure or a write failure,