Hello, This has never happened to me in years of using Macs with external drives. I have two bare 3.5" drives mounted in a caddy connected to my Mac. All has been fine for a few months. Yesterday I came back home and the lights on the front of the StarTech caddy were flashing orange. Subsequently found that there was only one partition showing in my finder sidebar. The drive had two partitions - one was a half terabyte partition with a clone of my Mac. The other was a 1.5 TB collection of media stuff. This partition simply wasn't there anymore. I tried disk utility and it says the drive is fine. But when I click on partition it now shows only 1 partition. The other has seemingly disappeared. From a bit of reading it seems as though all that stuff is still on the drive, but that the partition map (or something like that) has been corrupted somehow, and now that partition is not able to be seen or accessed. Beyond that I have so far drawn a blank, other than some incredibly complex Terminal-level directions that I think were to do with re-building the partition map, but to be honest I wasn't so sure what they were for! At the moment I am running something called Yodot Recovery Software which I found after someone had asked about this exact same problem - so far it is still running but saying it needs 23 hours still to go! Can anybody help me with this problem? Running Mavericks on a 2009 MacBook Pro. I would hugely appreciate any help.