Dawning Of Holographic Media
Data recording can be fascinating—some methods more so than others. Drawing and writing was the earliest method. In 1877, Thomas Edison's tin-foil phonograph recorded sound by indenting the vibrations of a voice onto a tin-foil cylinder. In 1900, a device called the telegraphone recorded sound on steel wire by running the current from a microphone through an electromagnet while drawing the wire past it. Demagnetizing allowed the wire to be reused. By 1927, paper and plastic tapes coated with powdered magnetic materials were being used in place of wire. Then came along laserdiscs, invented in 1958, which contained a reflective layer embedded with data pits that can be read by laser.
As different as each of those recording methods are, the one thing they all have in common is that they record data on the actual surface of the medium. No matter how tightly each method packs in data, they are limited in capacity by surface area. Hitachi-Maxell's new holographic storage technology however, eliminates the areal density barrier by storing data through the full depth of the medium.
For this emerging technology, Hitachi-Maxell is partnering with a company called InPhase Technologies. Hitachi-Maxell is making the media, while InPhase is fabricating the drives.
Holographic storage not only increases capacity, it also speeds up transfer rates. Most recording technologies record data one bit at a time, but holographic technology allows a million bits of data to be written or read at once in parallel.
A single laser beam is split into two: a signal beam and a reference beam. A Spatial Light Modulator (SLM) encodes data on the signal beam by translating zeros and ones into an optical checkerboard array of approximately one million bits. A hologram that forms in where the two beams meet is stored via a chemical reaction in the light-sensitive storage medium. Multiple holograms can be stored in the same physical space within the medium by varying the angle of the reference beam. Data is read by deflecting the reference beam off the hologram, which is projected onto a detector that reads the data in parallel.
Holographic storage technology is well-suited for both enterprise and consumer use. The technology is ideal for video production and distribution and for storing vast amounts of data, regardless of type. Unalterable Write-Once Read-Many (WORM) media will allow compliance with Sarbanes-Oxley and other government regulations. The storage capacity of a single, 300-Gbyte cartridge is approximate to a half million 300-page books or 35 hours of broadcast-quality video.
In late 2005, Turner Broadcasting became the first television network to air content stored on holographic media. Using a prototype drive made by InPhase, a commercial stored on a holographic disk as a data file was migrated to a server for playback at air time.
With an expected ship date by the end of the year, the first-generation holographic media will have a storage capacity of 300 Gbytes per cartridge, a transfer rate of 20 Mbytes per second and an average seek time of 250ms. Although the media is WORM, rewritable media is in the works. The media has a three-year shelf life prior to recording and an archival life of more than 50 years after recording. No special handling is required. The holographic media cartridges measure 5.31 inches wide by 6 inches deep by 0.43 inch high and contain an optical disc with a diameter of 130mm. The media does not need to spin when recording and reading. Although the prices are yet to be determined, it is expected that the media should have the lowest cost per gigabyte of any commercial quality removable storage.
InPhase's Tapestry HDS 300R drive measures 5.75 inches wide by 5.25 inches high by 26 inches long. It will be available with SCSI Ultra-2, FC, FTP and Gigabit Ethernet interfaces, and in desktop, rack-mount and library configurations.
Second-generation holographic media, expected to be shipped in 2008, will have a capacity of 800 Gbytes per cartridge and a transfer rate of 80 MBps. The third-generation, expected in 2010, will have a capacity of 1.6 Tbytes per cartridge and a transfer rate of 120 MBps. Clearly, this is groundbreaking technology and one that enterprise organizations will be eager to get their hands on.