Q Could I partition a Western Digital 3 TB My Cloud drive?
A Not at present.
Despite their evocative name, at their heart these are Network Attached Storage (NAS) systems, with custom software that allows access from outside your network, and packages that share the storage facility across a range of different platforms and users in an attractive manner.
As a NAS, it runs its own OS, claimed to be Debian Wheezy, with software overlays to present its facile front end. This is quite different from networking external hard drives from your Mac, over which you retain full control.
Unless the vendor provides tools in their software to partition the drive, you are unable to do so, and there appears to be no way of doing this using Western Digital’s current products.
Comments A Unix/Linux wizard might be able to use the secure shell, SSH, in Terminal to connect to the drive OS and repartition it from the command line, but that is not supported and could lose access to the partitions or the whole NAS system.
For the moment My Cloud drives are not intended to be partitioned, nor indeed formatted in any way other than that determined by the vendor. Attempting to do so could rapidly turn the My Cloud into a brick.
Updated from the original, which was first published in MacUser volume 30 issue 03, 2014.