How to tell a RAID disk is actually working?

My 8TB Thunderbolt G-Raid drive, formatted 01, used to show both 4TB disks on my iMac desktop and in the Mac disk utility and elsewhere. Recently, only one disk shows everywhere and I can’t tell which one. There are no red lights. I just want to be sure a second drive is actually duplicating the first one. In the Configurator it says “Protected - RAID 1, Capacity 4 TB, Online, and then Disks: 1, 2”. But I don’t understand why the disk image that once appeared on my desktop, in the disk utility, and in the System report doesn’t show up now? Is this possibly due to a Mac system upgrade to Mojave 10.14.1? My finder is set to show all mounted disks. Really, I’m just looking assurance that I actually have a backup.

By design when the drive is in RAID1 it will only ever show one drive. It is not supposed to show both drives because the computer shouldn’t know it has 2 drives. That is handled by the RAID itself.

Thanks Rydia! This is good to know. I’ve also learned that I can open the door on the drive and see the lights (when writing to the drives) on both of them. Not that intend to do that all the time…

I am sorry, but the answer given here is not satisfying. First I have spent hours trying to determine if the mirror is working, with no documentation from G-RAID/WD on how to do this or what a properly working drive looks like in either Disk Utility or the G-RAID Assistant, or more importantly what a non functional drive looks like. I need a way, other than “trust us it works” to determine if the mirror is working properly. I’ll note that the G-RAID assistant actually says “Slot 2 Empty”. This does not live me with a good feeling. Can I get some help please.

Eighteen months on, did you ever find out if there is a way of telling?

Yeah…I second that. Did anyone get any clarification on this? It just seems like a lot of trust when there’s no visual indication of the status of the mirror working correctly. The Assistant App telling me slot 2 is empty doesn’t really sit well :neutral_face: