The original 1TB HDD on my early 2008 8,1 iMac seems to be ejecting itself / disappearing when I am using Time Machine to save a large back up to it. The drive is about 8 years old and has been used daily for the first 6.5 years. It has spend 1.5 yrs in storage and was recently reinstalled into the iMac. I reformatted the drive and partitioned it. When performing a Time Machine back up (250GB) to the main 750GB partition, it gets to about 180GB then the drive disappears /ejects itself, and cannot be found in Finder or Disk Utility, even after rebooting. It only reappears on booting up the machine from cold the next day. If I try the TM back up again, the same thing happens (ejects at around 180GB). Disk Utility shows no faults on the drive and I've repaired it several times using Disk Utility in 10.11, and also tried recreating the partitions and erasing their contents. I saw a thread that stated that DiskWarrior was the only way to fix the corrupt file system on such a 'disappearing' HDD. What do you think? Or is it a hardware fault? I have backed up my data elsewhere obviously. Thanks in advance!