In addition to the Drobo 5D attached via TB to my nMP, I have a simple USB3 enclosure with a 3TB NAS. The drive is partitioned: 2.25TB for TM and 750GB as a boot drive which is backed up nightly with CCC. In the last two weeks I've started having issues with TM just hanging. It'll get anywhere from a couple hundred KB to around 100MB into a backup and it'll just hang. It seems the only way to restart the backups it is to go through the procedure below: Turn off TM Stop using said disk (in TM preferences) Eject disk Turn off and on the power to the chassis Delete the *.inprogress backup Re-select the drive as my TM backup disk Turn TM back on and let it do it's thing All that and it works about 50% of the time...sometimes it takes a little more fiddling like restarting my entire machine Is this just a flakey USB3 chassis? Anyone else find USB3 external drives to be unreliable? Is this a nMP issue others are having? I don't know how much this bears on my issue, but my TM backups are set to backup my entire boot drive along with a few directories on the Drobo such as iTunes, iMovies and Pictures.