A new DVD defect management study, conducted by Media Sciences, and sponsored by the RAM Promotion Group (RAMPRG), reveals that DVD-RAM drives provide the most robust, drive-based defect management among currently available recordable DVD formats. An optional protective cartridge offers even greater protection and reliability for DVD-RAM.

A new whitepaper, Defect Management Capabilities of Various DVD Technologies by Media Sciences, an internationally recognized, independent testing laboratory, outlines an investigation into three formats of rewritable DVD drives and media including DVD-RAM, DVD-RW and +RW. The investigation focused on overall defect management, compatibility, media defect and error detection/correction, and looked to identify the pros and cons of defect management currently available to users.

"With so many recordable DVD formats available, we wanted to investigate the current differences in defect management technology," said Dr. Jerome L. Hartke, President, Media Sciences, Inc. "What we found is that while no two devices or media are the same, DVD-RAM currently offers the best available defect management for rewritable DVD applications."

The study focused on the two different drive-based defect management methods -- slipping and linear replacement. Slipping works by marking a defect and sequentially moving data to the next good region. By contrast, linear replacement marks the defect and moves data to a non-contiguous, designated spare area.

The study finds that DVD-RAM, which employs both slipping and linear replacement, offers a high level of data integrity on full random access media. By marking the defect and finding the best-allocated area for continuous recording, DVD-RAM allows users to have a higher level of confidence in data storage and retrieval.

"Defect management is one of the key functionalities that has led RAM Promotion Group member companies to support the DVD-RAM format," said Tony Jasionowski, Executive Technology Director, RAMPRG and Senior Group Manager, Panasonic Technologies Company. "DVD-RAM supports a powerful, drive-based defect management system that has been available for more than 5 years. This, coupled with all of the features that DVD-RAM media and product offer, make it the best choice for DVD recording today and for the future."

In addition, the study showed that while other media formats employ some defect management capabilities, they don't deliver across the board. For example, DVD-RW drives flag, but do not replace defective sectors and are designed more for sequential recording, such as streaming A/V. Therefore, because drive-based defect replacement is not available, the study finds that DVD-RW disks may not be suitable for computer data storage. The study notes that standards for +RW media do not define a defect management system, but instead defer to a future planned Mount Rainier standard (+MRW) that is drive-based and requires a compliant write drive and recording system. +MRW awaits planned recording drive and operating system support.

Beyond detecting errors and relocating data to a defect-free area, the study determined that defect management can also compensate for the gradual degradation of the media that is a normal result of repeated overwrite cycles. This protection, and a unique recording layer and randomization of overwrite locations on DVD-RAM, adds to the longevity of the media which allows over 100,000 overwrite cycles.