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What is DVD-RAM?

DVD-RAM is a high-capacity, high-performance optical disk that allows data to be read, written and erased. It is designed to work exactly like a floppy disk, allowing users to copy and delete files from it, and use it to run programs. DVD-RAM offers all of the benefits of DVD ­ including high capacity and compatibility with CD formats ­ combined with enhanced rewriteability.

With current capacities of 2.6GB to 5.2 GB per disk, DVD-RAM offers up to eight times the storage of a rewriteable CD. The growth path for DVD-RAM takes capacities even higher to 9.4GB per disk. In addition, DVD-RAM is much cheaper than conventional magneto-optical drives. At less than one penny per megabyte, it is the most economical rewriteable medium available today. Also, it can read all of the CD and DVD formats including CD-ROM, CD-Audio, CD-R , CD-RW, DVD-ROM and DVD-R, making it an ideal choice for high-density data storage and exchange.

Technology Overview
DVD-RAM drives use phase-change technology in which a laser heats the inner surface of the disk to magnetically charge it. This allows the data to be rewritten hundreds of thousands of times. A "wobble-land-groove" format provides clocking data, with marks written on both the grooves and the lands between grooves. The grooves and pre-embossed sector headers are molded into the disc during manufacturing. The DVD-RAM wobble-land-groove format or track structure makes DVD-RAM technology reliable, and the constant linear velocity format provides high access speed and capacity.

DVD-RAM discs consist of double layers of metallic film embedded in hard plastic. The drive motor constantly changes the disc's rotational speed to compensate for the location of data on the disc. A laser uses light of varying intensities to write and erase data. The metallic layers in the disc are made of a crystalline material that reflects light the way a mirror does. To write data, the laser heats a metallic layer to 900 to 1,300 degrees Fahrenheit and creates pits in the surface. To erase or change data, a weaker laser beam heats the pits to approximately 400 degrees Fahrenheit.

Single-sided DVD-RAM discs come with or without cartridges and can be read by some "newer generation" DVD-ROM drives (check your drive's specification for additional info). There are two types of cartridges: type 1 is sealed and type 2 allows the disc to be removed.

Available now, single-sided DVD-RAM discs hold 2.6GB of data. Expected to be available in Q4 99, single-sided 4.7GB DVD-RAM disks achieve their high storage capacity from a decrease in track pitch and pit lengths, allowing for a higher density media. Today, the minimum pit length of a single layer DVD is 0.4 micrometers, as compared to 0.83 micrometers for a CD. In addition, the DVD track pitch is reduced to 0.74 micrometers, less than half of CDs 1.6 micrometers. With the number of pits equating to capacity levels, DVD's reduced track pitch and pit size creates four times as many pits as CDs.

The transfer rate for DVD-RAM is determined by the media specification. The 2.6GB disc has 1,385KB/sec. transfer rate, and the 4.7GB disc will have 2,770KB/sec. transfer rate. Access times will also evolve with an increase in disc rotational speed, reducing drive latency. Further reductions in access time will come from mechanical improvements, a more robust servo technology and mass reductions in the optical pickup.

Writeable Formats
Several DVD formats were developed and standardized by the DVD Forum to meet a variety of write-once and rewriteable needs. These formats include DVD-RAM, DVD-R, and DVD-RW. The following table summarizes the differences between these formats:

 
Format DVD-RAM DVD-R DVD-RW
Availability Now Now Now
Description Random access storage similar to floppy disk or CD+RW. Write-once. Provides sequential write, similar to CD-R. No overwrite capability. Limited sequential rewriteability.
Capacity/Side 2.6GB/side 3.95GB/side 3.95GB/side
# of Rewrites 100,000 0 1,000
Write method Wobble-land-groove N/A Wobbled groove
Drive price $500 to $700 $17,000 $3,000 to $5,000
Media price $25 around $100 $45
Applications Storage, Backup, Archive, Internet, Video Pre-mastering Mastering and Authoring

 

While there are specific areas for which DVD-R and DVD-RW are best suited, DVD-RAM is the only writeable DVD standard that will fulfill the requirements of mass commercial and consumer audiences. DVD-RAM differs from the other writeable DVD standards in several ways. Firstly, it provides random access rewriteability, like a floppy disk drive, making it perfectly suited for use and re-use by consumers. The low cost of both the drive and media make it a natural choice for a wide audience of users, even those that are value-conscious. With support by the DVD Forum and a strong feature-set, DVD-RAM is anticipated to continue as the leading re-writeable standard.

Market Demand and Outlook
DVD-RAM drive shipments began in 1998, and more than 100,000 units were shipped that year. Research firm Disk/Trend expects phase change drives to be displaced by DVD-RAM drives after 1999, and DVD-RAM to begin its run as the dominant product in 1999. Disk/Trend predicts that DVD-RAM will remain the dominant DVD rewriteable format due to its current market predominance, with major growth beginning in 2000.

Applications­ From Backup to Publishing
DVD-RAM is designed to playback all DVD-ROM applications as well as for desktop storage, data exchange, backup and archiving. Because of the wide variety of suitable applications, a DVD-RAM drive could be used as a viable replacement to do the job of several other devices, such as CD-ROM, CD-R, optical disk, tape, removable hard drive and floppy drive storage.

DVD-RAM is an excellent choice for backup and archiving. At less than a penny per megabyte, cartridges are extremely inexpensive. Given the well-established durability of optical media, they are also far more reliable than tape, the only cost-competitive alternative. And, because cartridges can be stored on the desktop, adding to archives or retrieving files from backup is infinitely easier than doing so from tape.

With their high capacity and rewritability, DVD-RAM discs have enormous potential for many markets, such as education and entertainment. They are also ideal for personal multimedia publishing, in applications such as presentations, sales tools, training and corporate communications. Future set-top box applications, which will give users the capacity and bandwidth to download their favorite movies, are also on the horizon. DVD-RAM drives are already being introduced in some personal video recorders as an alternative to tape. In addition, new DVD-RAM jukeboxes provide high-capacity, on-line storage for applications such as document imaging and image management.

Because they follow a standard format, all DVD-RAM drives and cartridges will be compatible with each other. This compatibility will further drive down prices, making the technology even more appealing to OEMs and consumers.

A DVD Forum approved format, DVD-RAM is a storage medium with a unique position in the high-capacity storage arena. It offers the "average" consumer an opportunity to afford high-capacity, rewriteable, removable storage for the first time. With the ideal mix of features at an affordable price point, DVD-RAM is well-positioned to become the medium of choice for high-density storage and exchange.

 

 

 
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