8/4 TB G-Raid formatted EXFAT raid 1 used with Windows over a year. Bought new IMac with High Sierra in October. The drive was read/writeable but within the last week two folders containing many subfolders by date containing my last two year’s work, ~300,000 files, disappeared. Just gone. No warning and not a trace anywhere including trash can. Immediately took the drive to local shop and the drive tested fine but the two folders were not visible, could not be seen or recovered. I’ve opened a ticket as it’s still under warranty but my question is path forward. Where do I go from here? I’ve not plugged it back in.