Add another disk

I have WD my passport ultra,I want to add him to my cloud to expand my space.
I can do this?

Yes. You can connect any USB external hard drive to the USB port on the back of the WD My Cloud device. You can then use the My Cloud Dashboard administration interface to further adjust access to that external USB drive’s content or backup the My Cloud, via Safepoint, to that external USB hard drive.

Please note that there are currently copying speed issues when copying data/files across the My Cloud’s USB 3.0 port.

http://community.wd.com/t/before-you-pack-up-your-wd-and-return-it-lets-talk-about-copying-speeds/91887

I get error mate,

A share could not be created on a USB device (vendor: Western Digital, model: My Passport 0830, serial number: ************, file system: ntfs, label: My Passport, share name: My_Passport).

Do you have another external drive you can test? For some, including myself, the WD My Cloud is failing to mount certain external USB drives. In my case I have two external drives that won’t mount but several others that will. I’ve sent logs to WD but haven’t heard anything back with a workaround or fix.

There is a similar recent thread where someone else has trouble with one of their external USB drives not being recognized or properly mounted.

http://community.wd.com/t/missing-share-query/140796