Something is off here.
diskutil cs revert /dev/disk6 and in the second, my macmini's USB controller stopped working and hard ejected (like pulling their plugs) all other attached USB devices.
Then I opened disk utility, and it repeatedly tried to mount them again only to see them immediately ejected again. This only happens with disk utility open.
Still, the USD interface seems to be completely unusable, not even keyboards are recognized, once the conversion process starts.
The reversion process seems to be active, but the affected HD's drive only blinks slowly and rhythmically. This goes for 24 hours now, and I have no indication about actual progress.
sudo diskutil cs list gives me this (disk id changed due to the unplugged other drives)
Disk: disk3 Status: Online Size (Total): 2999772905472 B (3.0 TB) Conversion Progress: Converting Revertible: Yes (unlock and decryption required) LV Name: Backup (Seagate) Volume Name: Backup (Seagate) Content Hint: Apple_HFS
I get no percent indicator as it seems to be visible, at least when encrypting or forward converting (according to several posts). Anyway 24 hours allows me to start worrying.
I wonder if it would not have been better to just copy the contents of the disk somewhere else, format the disk the way I want it and then to copy the data back.
The disk isn't mounted during the process and I do not know whether changes are live or are committed only at the end of it. Anyone with an idea, of what to expect (maybe that's normal) or of how to continue.
The disabled USB interface currently hinders me to do my job, which is worrisome.