I Have been able to use 2 external drives (WD My Book 4 TB) to work with my My Cloud. But when I tried to add a third identical drive it had lots of trouble keeping the drive recognized. The other day it refused to see the third drive even after I did a complete reset (the one where you hold the reset ‘button’ with a paper clip for 45 seconds while powering on. I have it working with the other two, but not the third. These are all WD drives less than a year old. You’d think WD products would work with other WD products of recent vintage. Is it the USB hub? It’s a Belkin 4 port powered hub I got at Best Buy. Is there perhaps a better hub that would be WD recommended?
Also, I have a WDTV Live which was working fine with the 2 drives attached but which started acting flaky with the 3rd drive attached. The WDTV live would suddenly stop playing videos and kick me back to the directory listing, or it would crash and reboot. I was beginning to think there was something wrong with the WDTV live. But when the 3rd drive stopped working altogether and I removed it from the USB hub the WDTV live started working normally again. Very strange.