I had wanted such a thing too, for reasons you specify and also because I would expect that it would be less loud than multiple spinning hard drives. Either one

I had wanted such a thing too, for reasons you specify and also because I would expect that it would be less loud than multiple spinning hard drives. Either one can fail and if so then the data from the remaining working one can be copied onto a fresh SSD or hard disk, I suppose. Combined with journaling file system can perhaps improve further. With appropriate considerations, you could recover after a power outage. (This might be able to be done without a specialized file system, although a driver and/or controller might be needed for the mirroring and access.)