Lately I have noticed that my High Sierra 17,1 iMac will restart on its on, or even shut down by itself. I booted from the internet and reinstalled High Sierra on my fusion drive. Then, I booted in both Apple+r and opt+r to run disk utility on my main hard drive, but Disk Utility cannot see the main fusion HD. So I booted from an external drive and repaired my fusion drive. Still concerned that with the new system install, Disk Utility cannot see my fusion drive, I called Apple Support. They told me to go to the Apple Store for repairs. There, they ran diagnosis software, that reported nothing wrong except my Ram may be seated incorrectly, but Apple Store said to let them wipe the fusion drive, because it will involve terminal commands. Then reinstall High Sierra. Has anyone w a fusion drive experienced this corruption updating to High Sierra?