Hi all, I have a late 2012 model iMac with a 1 TB fusion drive that was making some weird buzzing noises a few months ago, which I don't think were just fan noises. I ran some TechTool Pro tests at the time and got some bad block warnings about the hard drive, but life got in the way, so I just left it (while continuing to back it up). Since then, the noises have stopped, but two days ago, my iMac died in the middle of doing a SuperDuper backup. I can still reboot it and do some things, like open Safari and other recent apps, but if I go to explore files in the Finder, it will hang and beach ball in certain folders, and either stay that way forever, or the iMac will crash entirely/restart. This leads me to think it's the mechanical HDD part of the fusion drive, and the SSD part is fine (booting works and recent apps sort of work). I also tried running EtreCheck, but it hung and beachballed on "checking hardware", and I had to force shutdown. Is there any definitive test I could use (or better yet, a bootable utility I can put on a flash drive) to determine if it is the fusion drive, before I delve into cutting my computer open? Thanks.