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:

The thought at that point is that these plates cooperating will have the speed and additionally unwavering quality of a more costly circle Upsers.

You can save a test file , an image works well, then eject and turnoff the g-drive ,remove one of the trays , turn it back on with the drive out and check the drive for the presence of that image on the running tray/disk.

Then repeat the above this time reinserting the tray and removing the other tray and power up. The test image should show in both drives meaning they are mirroring the data.

If you are using RAID 1 and one of your drives fail , the Mirror will be degraded ( And the failed drive will show red light) but can be rebuild from the good drive ( That still shows blue light ) .

The configurator utility will detect the degraded condition and will offer a “REBUILD” button that is normally grayed out when the status is “Protected”. If you press it it will rebuild the Mirror but it can take a long time since it will be copying everything from one drive to the other. After the rebuild starts it will show the progress and the rebuild button will be grayed out again .

I don’t think you can stop this process, not even by quitting the configurator . when you open it again it will show the ongoing rebuild process that kept going when it quit . It seems that the drives are still usable for read and write but it will only prolong the process as it will have to create a mirror of whatever changes you make.