This small program for testing is available directly from the manufacturer of the hardware and does not require a backup software.
You can download it here.

After the installation as an administrator on the server, run the itdt.exe.
(It is necessary to stop all services of the backup software before!)

Select L to go to the last page of the license agreements.

Then confirm with i.

Select S to search for available drives.

Select your drive, in this example 2. You get a X in column #.

Then enter a D to create a Dump.

After every test, the created files are shown and now you can go to the previous menu using the return key.

The created logs are located  in the "Output" folder. This is automatically created in the directory folder where you first run ITDT.

For further diagnostics:

T, to start the standard test.
To start the Full Write Test change the few with O (letter O) into the second-level menu and select W to start the write test. Choose the option uncompressed + 64kb. (This test may take several hours.)