The referenced Primus above is specific to the VNX (Unisphere v1.1).  Unlike in Unisphere v1.0 (or "Celerra Manager" for those that haven't yet upgraded) which had as part of the system initialization created a "root" user that could be used to log into the GUI, the VNX did not do the same and had to be manually created per the KB article.  Without the "root" user, in Unisphere (or Celerra Manager), you'd find certain tasks couldn't be performed in the GUI such as:       The user would simply be presented with uneditable text fields.   As for the original poster's observations, even as "root", the GUI never allowed for the deletion of any system generated volumes such as those of type: disk (and meta or slice as created automatically when creating filesystems); and therefore, attempts to delete a dvol would be halted as the "Delete" button or context-menu entry is greyed out.  Therefore, if you need to delete a dvol to in turn free up the underlying LUN, your only option is to do so from the CLI as follows:       or, simply            (-unbind) effectively consolidates steps #2 and #3 above   As for the "Delete" in the GUI in reference to Volumes, it is only available for user-created volumes such as those of type: stripe, meta, or slice manually created from existing volumes.
How can I delete\remove a volume from NS120 using Unisphere GUI?  I ensure that no filesystem exists on the volume\disk that I want to delete, however after this, when I select the disk\volume it seems that the delete button is greyed-out. I though this could have been user permissions, but logging in with root, I am still unable to delete.  I am capable of deleting this using the nas_disk delete command in the CLI - with both accounts (nasadmin or root).
Delete a disk\volume from NS120 using Unisphere GUI