PR2100 Can only seem to use one of the 2TB drives

I am completely new to using NAS drives. My PR2100 only shows capacity for one of the 2TB drives not
both on the dashboard can anyone confirm that this is correct. In the storage section it says that both drives
are working correctly.

Unless you changed the RAID mode when you set it up, it came out of the box in RAID1. In RAID1 mode, the drives are mirrored to each other. So if you purchased a 4TB PR2100, it has 2x2TB drives, and those drives are mirrors, so you can only access 2TB total space.

If you want all 4TB available to you, you’ll need to change the RAID mode to RAID0. But keep in mind, changing the RAID mode will wipe all of your data.

This is brilliant I am very grateful for the information. Am I right in thinking then that the data on drive one
is duplicated on drive two. If this is the case I am happy as I just wanted to be sure that everything was
backed up should drive one fail. I also have another back up off site.

Thanks again for your help.

Yes, mirror mode = duplicate data over all disks.