Hello,
I recently purchased a 4tb WD elements for my WD my cloud home (3tb) and I want to use the new drive to expand my old drive. Can this be done or do I have to purchase another WD my cloud home in order for this to work.
You can certainly plug the 4TB WD Elements into the USB3 port of the MCH and manually copy files over at a very fast speed (up to 130 MB/s). However, there is no automatic way of using the USB HDD as data and program storage for your programs, in fact the USB drive is not mounted or seen by the OS (either Win or Mac) and only accessible through the web app or mobile app.
OK I will have to buy another NAS but thank you for the info.
Have you looked at the User Manual?
User Manual: My Cloud Home and My Cloud Home Duo (westerndigital.com)
I have and watched several clips on Youtube. Apparently the option has been removed from the current WD OS.
