I was using OMV4 until a couple days ago, but my RAID 5 with 4 hard drives was not showing up in my OMV configurations any longer.
I then upgraded (reinstalled) to OMV5, but my RAID is still not showing up.
I tried to fix it through mdadm assebmling and it actually went through successfully (at least it looked that way to my newbie eyes), but as I tried to restart the machine, it would not even finish booting up. It gets stuck after init ramdisks with 4 errors "ataX: softreset failed (device not ready)".
As soon as I unplug one of the drives it shows only 3 errors and finishes booting afterwards.
These three drives (plus my SSD) show up in OMV gui "Disks".