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Does anyone know a lot about mirrored external hard drives?


Well-Known Member
I use a 2021 iMac.
My pictures that cannot be fitted onto the internal hard drive are stored on three pairs of extra mirrored drives ( all set up by my wife)
When using two pairs of drives and copying from one to another one of one pair powered down. Both pairs showed up in a list of drives and folders. I wanted to disconnect the lot and start again in the hope that it corrected itself. I could not get them to disconnect so I powered the iMac down and hoped starting up again would sort it. Unfortunately neither pair will now show up on the list of folders and drives although all four drives will show up when connected on their own and the pictures seem to be present on each external hard drive.
All are Seagate 8tb expansion drives and were connected via the Belkin USB 3 hub recommended and sold by Apple and the hub is connected to a thunderbolt connection on the iMac.
Even connected to the usb ports without the hub it’s still the same and I’ve tried another iMac which shows the same.
1. Is this a common problem?
2. Is there a way of restoring the pairing without losing the data?