I have purchased a WD My Book 4 TB External Hard Drive USB3 and a Mac Book Pro 13 inch. When I plug the HD in the USB port (possibly USB2), it is recognised on the desktop but takes longer, sometimes up to 5-6 minutes. The HD has only 2TB data on it and still capable of 2TB more storage. Is it a normal function of taking that long each time you connect the HD to a Mac Book? Does the time taken to recognise the HD on the Mac is proportional to the amount of data stored on HD or should not make any difference? Please advise if something is wrong with the HD or the Mac.