Sony and Panasonic have developed a disc format for archiving data that starts at 300GBytes and runs up to 1TByte.
The write once technology (which used to be called WORM - write once, read many) is a double-sided, three layer disc written by a 405nm laser. It uses Reed-Solomon encoding, writing data in 79.5nm bits on a track pitch of 0.225micron.
The two companies have agreed on a crosstalk cancellation format that electrically removes crosstalk from the adjacent tracks. This crosstalk increases as the track pitch becomes narrower, so the cancellation allows higher quality playback performance. They have also added Partial Response Maximum Likelihood (PRML) signal processing that takes inter-symbol interference into account, again allowing the discs to reach the 1TB capacity.
Data center operators have been struggling with the long term archiving of data, particularly images. Using archive discs cuts the power consumption against storing infrequently accessed data on hard drives. In recent times, demand for archival capabilities has increased significantly in the film industry, as well as in cloud data centers that handle big data, where advances in network services have caused data volumes to soar, says Sony.
Facebook for example has developed a storage system that uses 10,000 Blu-ray discs to hold 1PB of data. This uses a rack of 24 magazines, with each magazine holding 36 cartridges and each cartridge holding 12 Blu-ray discs, for a total of 10,368 discs. A robotic picker goes to a specified magazine and then locates a cartridge and selects a specific disc.
Currently a prototype, the company is looking to share the design with the Open Compute Project to get it into production as it cuts the cost of storage by 50% and the cost of power by 80%.
The archival discs will also allow inter-generational compatibility between different formats, ensuring that data can continue to be read even as formats evolve. This makes them robust media for long-term storage