What is DVD RAM exactly?

[Cobra281]

just thought i'd ask guys... i have a LG GSA-4040B and it has DVD±R(W) / DVD RAM... what is the dvd ram exactly? i started to wonder after i noticed my cd\dvd burner drive on my computer is labeled as DVD-RAM Drive (D:)

[ClayBuster]

https://www.videohelp.com/glossary?D#DVD-RAM

[tompika]

Nic Wilson (the author of DVDInfo PRO) wrote
http://www.netfarer.com/forums/index.php?


What is DVD-RAM?

DVD-RAM is a re-writeable, re-recordable DVD optical disc that is designed to be written, read, erased and re-written again and again. It is designed to operate like a floppy disc drive or hard disk drive. The current capacity of DVD-RAM is 4.7GB for a single sided disc and 9.4GB for a double sided disc. Earlier generations were 2.6GB / 5.2GB respectively. DVD-RAM is backwards compatible with other formats such as CD, CD-R. CD-RW. DVD-RAM is very durable with 100,000 re-write cycles and greater than 30 year life span.

DVD-RAM comes in two types, those with cartridges and those without. Earlier models of DVD-RAM used cartridges and the discs were not removable from the cartridge. Type 1 is double sided and Type 2 are single sided. Later versions allowed Type 2 discs to be removed from their cartridge but not Type 1. Recently however this has changed again and drives such as the LG GSA-4040B only accept them without the cartridge. Some DVD-RAM discs are now supplied without the cartridge while others still supply them with it, but allow the disc to be easily removed. Remvong the disc from the cartridge is a very simple process of popping a pin and opening the case.

How does it work?
DVD-RAM uses a phase change material which is different from the dye type material that CD-R. DVDR uses. A laser is used to heat the material to approximately 900 - 1300 degrees F, which alters the materials characteristics from shiny to dull. If the disc needs to be erased, the laser heats the disc to about 400 degrees F which returns the material to it original shiny state. The shiny and dull areas are then converted into usable information. The capacity of the disc was increased to 4.7GB per side by narrowing the track width and decreasing the laser spot size.

How is it different to DVD-RW or DVD+RW
One major difference is DVD-RAM is a true random access device just like a hard disk. This allows DVD-RAM to be significantly faster at retrieving data than other formats. Another major difference is DVD-RAM is a more durable with a re-write rating of 100,000 cycles compared to a mere 1000 of DVD-RW or DVD+RW and a more robust design than its competitors with DVD-RAM having nine internal recording surfaces compared to three of DVD-RW or DVD+RW. DVD-RAM uses metal alloy which gives it its greater number of re-write cycles. DVD-RAM also uses a very sophisticated ECC error correction scheme making it ideal for data storage.

DVD-RAM is very versatile. For example, a new DVD-RAM disc can be quick formatted under Windows, using windows standard format as you would for a hard disk. (DVD-RAM is also compatible with Apple Mac OS in this regard too). As soon as the brand new disc is loaded, windows sees it as a valid partition of 4.7GB. It can be formatted as FAT32 using quick format which takes a few seconds. It is then ready to be used just like a hard disk without any other software requirement that other formats need such as packet writing software or similar. The above is simply not possible with DVD-RW or DVD+RW, both of which require custom burning applications or packet writing software to make the disc operate like a floppy or hard disk, and still cannot be used as FAT32 like a hard disk. Even then its competitors require very long formatting processes, even though on +RW this format process is done in the background and hidden from the user, a section of the disc can only be written if it is formatted. DVD-RAM is a true random access drive, so the retreival of the data faster.

With the new DVD-Multi specification and logos, it is becoming easier for users to identify players that support this format for playback of video data. At this point in time these seem to be very limited.

DVD Recorders such as the LG mentioned above are a very good value for money as it is supports all of the DVD formats, DVD-RAM, DVD-R/RW, DVD+R/RW as well as all CD formats. As it costs no more than other drives which do not offer all of its features Its value is very good. Panasonic DVD-RAM burners at this state only support DVD-RAM, DVD-R/RW.

Data marks on DVD formats are placed along a continuous spiral track. On the DVD-RAM format these data marks can be placed both in the grooves and in the spaces between the grooves. This provides the opportunity for greater storage density. DVD+RW on the other hand proposes for data marks to be placed only along the continuous spiral track. This means that as storage density requirements increase over time, DVD+RW will be limited in storage capacity.

A comprehensive Defect Sector Management (DSM) is incorporated into DVD-RAM. This is very similar to the system used by hard drives. This ensures that data is not written to a defective area of the disc. DVD-RAM uses redundant addressing and redundant timing information which allows for data recovery to be more reliable. If an address sector is not readable, the sector can be found using the last good address and time between address sectors. Damaged user data can be recovered using the DVD ECC (Error Correction Code).

An example Media Info from a MAXELL 3x DVD-RAM disc is shown below:

MediaCode MXL8
Format Capacity 4.27GB(4.58GB)
Book Type DVD-RAM
Media Type DVD-RAM
Available Write Descriptor ZCLV 3.0x 4155KBps
Data area starting sector 31000h
Data area end sector 22211Fh
Linear Density 0.280um/bit
Track Density 0.615um/track
Number of Layers 1


Pros
High data security
Rewritable 100,000 times!
Drag & Drop – just like a hard disk
Fast, random access
30 year media life
Cartridge option (on some drives) to protect valuable data.
No additional software needed.

Cons
Limited popularity at the moment in some areas.
Limited distribution of media in some areas.
Media Cost higher, although I have reports of caddlyless media getting cheaper.

Cheers
NicW

[au7usa]

Would it be considered a removable hard drive then, does the firmware report it as such?