Yosemite Server Backup 8.1 and above.
You can delete Virtual Library Devices (VLDs) by expanding down from the devices view on the main Yosemite Server Backup window. Then right-clicking on the object and selecting Stop. Once stopped, you can then right-click and delete the VLD. However, doing this does not remove the backed up data. You can remove the data manually or you can run an erase on the VLD prior to deleting it.
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