Professional Disc for DATA
From Wikipedia, the free encyclopedia
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| Media type: | Optical disc |
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| Capacity: | 23 GB per layer |
| Developed by: | Sony |
| Usage: | Data storage |
Professional Disc for DATA (PDD or ProDATA) is a recordable optical disc format which was introduced by Sony in 2003. It was one of the first two formats (along with Ultra Density Optical) to utilize blue-violet lasers for reading and writing, which allowed for much higher density data to be stored on optical media compared to the higher wavelength infrared laser technology used in the CD and red laser technology used in the DVD format.
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[edit] Technology
PDD uses a 405nm wavelength and a numerical aperture (NA) of 0.85 for the laser, allowing 23GB of data to be stored on one 12cm disc - the equivalent to nearly five single-layer DVDs, and a 1x speed data transfer rate of 88Mbit/s for reading and 72 Mbit/s for writing. Plans were also made to introduce dual-layer 50 GB and quad-layer 100 GB discs in the future.
Confusingly, this sounds very similar to the Blu-ray Disc format, another optical disc format using blue-violet lasers which is also supported by Sony. Even the PDD's caddy and Blu-ray's prototype caddy (later it was dropped) looked very similar. The only apparent difference is that single-layer PDD discs have a capacity of 23 GB whereas Blu-rays can store 25 GB. However, Blu-ray Discs only currently allow a 1x data transfer rate of 36 Mbit/s - much lower than PDD. This is because PDD discs use much higher quality media and drives use higher quality components, making them prohibitively expensive for the average consumer segment to which Blu-ray Discs are aimed.
[edit] Applications/Products
PDD drives and media became available in mid-2004; the format was aimed primarily at small and medium-sized enterprise for data archival and backup. The BW-RS101 external SCSI-3 drive originally retailed in the UK at £2,344 (excl. VAT) directly from Sony, and 23 GB write-once and re-writeable media retailed for £30 each. Two other drives - the BW-F101/A internal SCSI drive and the BW-RU101 external USB 2.0 drive also became available around the same time.
The PDD format is also used as the primary recording medium for Sony's XDCAM professional video format, with the format using PDD discs for recording & playback of MPEG-2 or DV-encoded video data.
