available for optical media range from ISO standard technologies like UDF to proprietary formats. File tracking Optical library management software will often track the files and folders extant on a piece of optical media by means of a database. Any filesystem data pertaining to an individual media would be available in this database. For example: paths and names of files and folders, file sizes, and all of the metadata that a modern filesystem may keep. Access control Optical library management software makes itself available to the OS in an assortment of ways. One of these ways in a Windows environment, is by way of virtual drive letters. Essentially, the whole of an optical library can be viewed, read to and written to via a virtual filesystem while the management software handles all of the media movement and I/O requests invisibly in the background. Another way that access to the optical library may be accomplished is by way of CIFS shares (more often seen with Unix-type optical library management applications). Access time issues All the jukeboxes work best when only a few users need to access the discs at the same time. Small jukeboxes have only one or two CD, DVD, UDO or Blu-ray drives, so only one or two users can share the jukebox at the same time. If additional users want to use a new disc, they have to wait for the disc to be swapped by the robotics in the jukebox. This takes from 4 to 9 seconds. Larger jukeboxes have six or more readers, so more users can simultaneously access the different discs at the same time. A more efficient recommendation is to have a disk cache attached to the jukebox for a higher number of simultaneous users. This way, the configuration operates in a FILO (First In Last Out) Manner. Here, files accessed are only sent back to the optical discs after they have been utilized. Changes may or may not be saved or versioned based on the user configuration and accessibility settings on the storage management software that runs the optical jukebox. The number of drives in the jukebox can be up to six depending on the size of the jukebox. The drives will read and write the data to the RAID / Disc cache and then present to end users. This way the 4–6 seconds read time only occurs during the initial data read