When you are first configuring the VLD for use, you only need to pay attention to the 'Storage Folder Option', 'Virtual Media Drives', and 'Virtual Media Slots' options on the Library Configuration page in the VLD properties. The 'Virtual media status' and 'Virtual media maintenance' sections are used to move a VLD from one location to another and can be safely ignored.
Storage Folder Options: this section allows you to tell NovaBackup Network where to write date. You can supply up to four different folders. The folder(s) should be on a local disk (because of permission issues with the NovaBackup Network service accessing a UNC path).
The capacity field allows you to put a maximum cap on how much space will be used in that folder. When that space is used, NovaBackup Network will tell you the media is full.
The Used field reports how much space is being used. This field is a bit misleading. The VLD allocates space in 1GB chunks. When a backup runs it will use at least one chunk. Even if the backup is only 1k, the backup uses a chunk and another backup cannot use the rest of it. So your reported used space may be somewhat higher than you expect.
The Min. Free field allows you to ensure that there is a minimum amount of space on the folder where the chunks are so you don't overfill the target disk.
Virtual media drives: this setting allows you to emulate a multi-drive loader. Increasing this number may increase backup performance. And it will allow multiple jobs to use the VLD at the same time
Virtual media slots: this settings determines how many virtual media you can have. The VLD is designed to emulate a physical media loader. Each virtual media slot "contains" a virtual media. You should choose a number that is greater than or equal to the number of media your backup rotation required. No space is allocated or consumed when you set this value so there is no harm in setting the number higher than you need.
Virtual Tape Library on Network / NAS
By default NovaBackup Network service uses local system which does not have rights to network share.
Run the NovaBackup Network service as a user that has full admin rights to access local computer and the Network / NAS share....or make sure the Network / NAS share has no write restrictions.
Make sure that the Virtual Tape Library uses the correct path to the Network / NAS boxes. (eg. \\NASname\sharename ). Also make sure you initialize the Virtual device
How a VLD differs from a physical loader
When a backup writes data to a virtual media, the data is written to files in the storage folder(s) rather than to a physical tape. The virtual media only uses the space it needs. Unlike physical tape where a small backup will leave a large amount of tape unavailable for other backup sets in a rotation. Likewise, you run out of space in the storage folder, a virtual media will expand to be as large as the backup data without ever spanning to a new virtual media.
Hopefully this helps clarify how the Virtual Tape Library works.