As added information after some attempts I also managed to re-create the RAID using 4 WD40EFRX WD red drives. The re-create function (via USB key) was somewhat unpredictable but it worked after having diskpart cleaned the 4 disks (on another machine). Then I created the USB boot from a 1.7.6.21 virtual DVD (with amended whitelist.xml) and I simply amended the two WHITELIST*.XML files on the USB stick replacing one of the 4 Tb entries with the WD RED model number. In some other attempts with almost identical configurations I obtained either BAD CONFIG errors or other strange errors. It is really difficult to understand what I did wrong. In another test I did it looks like the 6 Tb HD was recognized as such, but I need to make a dedicated install to be sure a 24 Tb RAID 5 NAS (18Tb of data) can be used on the DX4000.
