I am posting this here because I am not sure if this is a device-specific issue, or if it is a software issue, and i wanted to se if anyone else is having this problem. I have the new 2013 iMac, with a 256gb SSD. For bulk storage, I have been using a 3tb external USB3 hard drive. This drive seems to be working perfectly. The problem, is with spotlight. Every night now, after midnight, is when I have been noticing it. I will hear the drive chugging along like its working on something, even though I am not actively reading anything from the drive. When I click on the spotlight icon, I see a striped bar and "Estimating indexing time", which never goes away and never stops estimating. I first noticed this a few days ago, and (after much research) found the following fix: http://apple.stackexchange.com/questions/1072/spotlight-indexing-appears-stuck-what-can-i-do The fix is the top result with 14 rate ups, where you turn off indexing, delete the index from the external drive, and restart indexing. This worked, after about 30 seconds of indexing the drive was fully indexed, and I could search for any file as I should. Also, the next day when I turn the computer back on again, the spotlight index still worked fine, I could still search for anything. HOWEVER: Again, late in the evening, I notice the drive working hard. WHen I check spotlight, it is again "Estimating index time" and the searches for files that worked earlier in the day no longer appear in the search. The only fix, is to re-do the steps in the guide I linked, but I would rather not do this on a daily basis... It would seem as if the spotlight index on the external drive is becoming corrupted on a daily basis... but not upon a restart, it seems more time-related.... its wierd. So, does anyone know of any solutions to this? Long term ones I mean. Thanks! Edit: I can of course fix it by adding the external drive to the 'privacy' tab of spotlight, so that it does not get indexed... however I don't really see this as a viable solution.