NOTE: There's a TL;DR section at the end of this post with required steps People with specific Seagate Ironwolf disks on LSI controllers have been having issues with Unraid 6.9.0 and 6.9.1.  Typically when spinning up the drive could drop off the system.  Getting it back on would require checking, unassigning, reassigning and rebuilding its contents (about 24 hours).  It happened to me three times in a week across two of my four affected drives.   The drive in question is the 8TB