Optical jukebox

An optical jukebox is a robotic data storage device that can automatically load and unload optical discs, such as Compact Disc, DVD, Ultra Density Optical or Blu-ray disc and can provide terabytes (TB) and petabytes (PB) of tertiary storage. The devices are often called optical disk libraries, robotic drives, or autochangers. Jukebox devices may have up to 2,000 slots for disks, and usually have a picking device that traverses the slots and drives. The arrangement of the slots and picking devices affects performance, depending on the space between a disk and the picking device. Seek times and transfer rates vary depending upon the optical technology.

Jukeboxes are used in high-capacity archive storage environments such as imaging, medical, and video. Hierarchical storage management is a strategy that moves little-used or unused files from fast magnetic storage to optical jukebox devices in a process called migration. If the files are needed, they are migrated back to magnetic disk. Optical disc libraries are also useful for making backups and in disaster recovery situations. Today one of the most important uses for jukeboxes is to archive data. Archiving data is different from backups in that the data is stored on media that will last up to 100 years. The data is usually written on Write Once Read Many (WORM) type discs so it can not be erased or changed.^[1]

Jukeboxes typically contain internal SCSI or SATA based recordable drives (CD-ROM, CD-R, DVD-ROM, DVD-R, DVD-RAM, UDO or Blu-ray) that connect directly to a file server and are managed by a third party jukebox management software. This software controls the movement of media within the jukebox, and the pre-mastering of data prior to the recording process.

Before the advent of the modern SAN and much cheaper hard disks, large-volume storage on DVD was more price-efficient than magnetic media. Jukebox capacities have greatly increased with the release of the 50 gigabyte (GB) dual layer Blu-ray (BD) format, with a road-map to increase to eight layers and 200 GB per disc. The current format, used in the DISC7000, allows 35 TB of storage from a single 700 disc jukebox. Optical disc libraries like the TeraStack Solution can store up to 78 TB of online and nearline data with a nominal power draw of 600 watts^[2]. These two units show the wide variance of product attributes.

History

One of the first examples of an optical Jukebox was the unit designed and built at the Royal Aerospace Establishment at Farnborough, England. The unit had twin read/write heads, 12" WORM disks and the carousels were pneumatically driven. It was produced to replace the 1/2 inch magnetic tape devices that were being used to store satellite data.

Special software drivers

Jukeboxes connect to a Windows, Unix, or other server using special software. The special software is not just a driver; it also includes a database that keeps track of the files on each of the discs. Users on the network can copy or drag and drop data to the server which automatically transfers the data to a CD, DVD, UDO or Blu-ray disc in the jukebox. The software also provides other functions including caching the data for both writing and retrieval functions, so as to improve performance. Currently, jukeboxes are now known as libraries as the terminology has changed. The jukebox hardware by itself is useless without software to comprehensively manage the appliance. Furthermore, speed and access time can be an issue if it is not properly configured.

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 6 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 process, then the data is sent to the cache. ^[3]

External links

• DISC Archiving Systems - BD Series (former NSM GmbH)
• HIE Electronics - TBYTe Optical Data Storage Product
• Sony CDL 1100 (Historic information from June 1998 about CD-Desktop-Library / Cygnet, Kodak and Elms mentioned)

References

1. ^ Mesnik, Bob "How to comply with the archiving regulations without paying an arm and a leg" http://www.imakenews.com/kin2/e_article000742009.cfm?x=b8v5FDQ,b25tl0b3,w
2. ^ Green Data Storage http://www.tmcnet.com/usubmit/2010/01/14/4572041.htm
3. ^ Gallen, Dennis " The Difference Between Jukeboxes and CD/DVD Servers" http://www.imakenews.com/kin2/e_article000654647.cfm?x=b8v5FDQ,b25tl0b3,w