I can't figure out how to add a 2nd disk to my DS223j and get it combined with the 1st disk into a RAID-1 configuration.
I got the DS223j setup with one disk just fine. I bought a DS223j and 1 new 4TB disk which I installed into my synology (it happened to go into the drive 2 slot rather than drive 1 but I don't know that that matters). That drive has been configured as Storage Pool 1 of SHR (Synology Hybrid RAID). I copied data to the Synology from 1 of 2 4TB disks from an old, fried WD MyCloud. That all seems up and running.
I'm having trouble adding a second disk and configuring it into a RAID-1 with the previous disk. I physically added the disk from the WD MyCloud to the Synology. I can see it under Synology's DSS (Disk Station Manager) -> Storage Manager -> HDD and it shows as healthy, allocation role '-'. I don't see how, though, to combine the disks into a RAID-1 configuration.
Please help.