Knowledgebase: Using disk drives
Understanding Virtual Jukeboxes
Posted by Sven Koester on 22 May 2007 13:12

When creating a Disk Storage for backup in the Storage Manager section, PresSTORE creates a virtual jukebox on disk (VJB).

Organization

A virtual jukebox is organized the same way as a physical one, so it behaves equally and can be addressed just like a physical media changer. It consists of a path on disk, where PresSTORE creates container files that can be regarded as virtual tapes. The number and size of the files are parameters in the virtual jukebox. By default PresSTORE creates 10 slots for 10 container files in a size range of 2 .. 1000 GB.

When creating the virtual jukebox, the container files can be created by labeling. Labeling means that just like on physical tapes, a label is written to the beginning of the container file so PresSTORE can recognize it. The file name that is used reflects the barcode of that virtual tape in the PresSTORE GUI. 

Resizing

Resizing a virtual jukebox is possible. Double click the virtual jukebox in the Storage manager and edit the values for the slot count and the size of the virtual tapes. The following items should be regarded:

  • When resizing a virtual jukebox, there can be no running jobs in PresSTORE that access the jukebox.
  • When changing the size of the virtual jukebox slots, existing virtual tapes are not resized immediately but when they are labeled the next time.
  • When reducing the slot count of the virtual library, take care that there are not more container files in the jukebox directory than there are slots. Otherwise it would be undefined which of the container files are accessible.

Drives

A virtual jukebox in PresSTORE is defined to have two drives. These are virtual drives to organize the access, it is not possible to change this setting. The drives do not reflect any physical number of disk drives; the two drives exist to allow restore operations during backup. By default, PresSTORE will use only one drive for writing, because write operations to both drives in parallel will not be faster than to one.

Replacing virtual tapes

The files used by a virtual jukebox are handled in the same way as physical tapes. To remove a tape in or out of the library, just move the file in or out of the jukeboxes directory. Do not forget to call the inventory function in case you moved the tapes manually. This behavior may be useful when the jukebox is located on a changeable hard disk:

  • Create the jukebox on an exchangeable hard disk
  • To extend the storage, remove the disk and mount another disk at the same location
  • Execute a jukebox inventory function


This way, one can manage multiple virtual tapes in the jukebox. Note that the directory configured a data directory in the jukebox setup in PresSTORE must be present in all drives.


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