Where is my second disk in RAID 1?


I have moved my 12 TB G-RAID USB3 nd Thunderbolt to RAID 1 and can only see one disk? How do I find the other 6TB disk?


What do you mean you can only see one disk? Where is this ‘seeing’ occurring? If you mean that you can only see the capacity of one disk, then this is normal. I assume your unit comes with 2 x 6TB disks, which provides a maximum usable capacity of 12TB (in RAID 0). When you go to RAID 1 you are mirroring, or copying the data twice across all disks in the set, which means you only get half the usable capacity (but you get fault tolerance). So 2 x 6TB disks in RAID 1 equals 6TB usable space (or a bit less after OS formatting).


Thank you I have misunderstood that and you have explained it to me. Just for clarity, I was only seeing one disk in my Mac’s disk utilities. Previously I had used a smaller model in JBOD mode and forgotten that was the case.

Thanks again for your help.



Yes in JBOD it will present in your operating system as a separate mounted volume for each physical disk.

In any RAID configuration it will present as one mounted volume (in your case, roughly 12TB in size in RAID 0 and roughly 6TB in size for RAID 1) despite the number of physical disks.

In case you are not sure about the different RAID levels, you want to always stick to RAID 1 (mirrored) with these type of 2 - 4 disk NAS / USB RAID enclosure devices.

People usually buy these types of devices to store data that is very important to them. Considering this, there is no real point in buying one to keep in RAID 0, because if any of the disks die, all your data is gone from all of the disks. You might as well just buy 2 separate USB 3 drives. These types of devices only really make sense in RAID 1 where the mirrored data is providing fault tolerance. That way if one disk dies the unit and the data will still be accessible on the other disk, or if the unit dies as well, just take a working disk out of it and attach it to a computer with a very cheaply sourced SATA to USB adapter which you can get online for £10 or less.


Again, thank you LD1, this is very helpful and I much appreciate you taking the time to teach me these things.

Take care,