hey Ozz,
I m using a USB connection. The same as I have been using for years over all OS since Tiger.
After posting my problem, I moved the external to a mini running Snow Leopard, all was good for a while. Mini and drive sleeping as they should.
But after 1 day the same problems started on the mini. I am suspecting iTunes as the culprit, which if is the cause will really **** me off as I mainly use my Macs for media sharing, I,E: mac ,itunes,AppleTV.
The most annoying thing is that once the Mini started to display these problems I have put the HD back onto the iMac running Yosemite, accepting that the eject and power off option was what I would have to put up with,..But hey, now everything is behaving as it should.
The external sleeps, imac sleeps and AppleTv recognises my library. I will not hold my breath as to how long this lasts, all os seem to be suffering from the same hassles with new iTunes updates.
I used to be a big proponent of Macs, telling people that they "just work" and were very user friendly, but unfortunately that belief is now gone.
I am not a fan anymore