whats the difference?

[excel8951]

whats the difference between "DVD-RW", "DVD+RW", "DVD-RAM", and "DVD-R" drives?

 

[GhostKat]

Each one of these is a format for a DVD disc. The RW ones are rewritable formats and the - and + specify that they are different in a technical way and are not compatible. The RAM one is a rewritable format also and is older. the R is a recordable only type where you can record once to it and that's it. They also have a - and + version of R out there.

Don't mind me I'm just posting so it doesn't say I'm a newb.

 

[orbz]

<A HREF="http://www4.tomshardware.com/storage/20030207/dvd_burner-01.html" target="_new">Link</A>:

<i>he Differences

There is very little difference between DVD-R and DVD+R, both of which can only be written once. They are used in exactly the same way. But you have to be careful with DVD-R because there are two standards for blank disks. The one to use is marked "DVD-R for General Use." The other is marked "DVD-R for Authoring," and it only works for mastering DVD video or data because its composition is different. This sort of DVD-R is not usually available to the general public.

Things get a bit more complicated with DVD-RW and DVD+RW. DVD-RW technology is very similar to that of the CD-RW. For DVD+RW, the Alliance wanted to make video recording easier, especially for home use. So they implemented a technology called Lossless Linking. In DVD+RW video format, a video can be encoded in VBR (variable bit rate). The process of writing at a constant rate takes up a lot of room, so it has to be stopped and started again. This is likely to cause link loss, which makes the disk incompatible with read-only devices like DVD video players. With DVD+RW, the process can be stopped and started again without any link loss. This characteristic makes the format efficient and suitable for random data writing and video applications. With lossless linking, it is also possible to replace any individual block of 32 KB (write unit) with another, without losing compatibility.

For a lossless link, each block of data must be written in the right place with precision (on 1 micron). For this, the groove is controlled by a high-frequency wobble (817 kHz at n=1) to ensure that writing stops and starts in an exact position. The writing clock resulting from the groove is very precise. At the same time, addressing information is stored in the spiral groove by locally inverting the radial wobble mark. There are four addresses per ECC block of 32 KB, so the address format is reliable with wide margins of detection.</i>

<i><font color=blue>There is no failure when you believe in success.</font color=blue></i>

 

[elzt]

In summary, there're 3 competing DVD recording standards:

(1) DVD-R and DVD-RW
~~~~~~~~~~~~~~
The first DVD recording format released and is supported by DVDForum.
DVD-R is a non-rewriteable format and is compatible with about 88% of all DVD Players and DVD-ROMs.
DVD-RW is a rewriteable format and is compatible with about 69% of all DVD Players and DVD-ROMs.

(2) DVD+R and DVD+RW
~~~~~~~~~~~~~~
Supported by the DVD+RW Alliance.
DVD+R is a non-rewritable format and is compatible with about 84% of all DVD Players and DVD-ROMs.
DVD+RW is a rewritable format and is compatible with about 70% of all DVD Players and DVD-ROMs.

(3) dvd-ram
~~~~~~~~
Supported by DVDForum. dvd-ram has the best recording features but it is not compatible with most DVD players and DVD-ROMs. Think more of it as a removable hard disk.


In addition, both DVD-RW and DVD+RW supports single side 4.7GB DVDs (called DVD-5) and double side 9.4GB DVDs (called DVD-10). However, DVD+RW has some better features than DVD-RW like CAV and CLV writing.


This site gives a more detailed discussion on the topic:

<A HREF="http://www.anandtech.com/guides/viewfaq.html?i=118" target="_new">http://www.anandtech.com/guides/viewfaq.html?i=118</A>

 

[ejsmith2]

Another note, albeit minor.

The DVD-ram disks are normally rated at 100,000 writes. The DVDRW disks (both plus and minus) are rated for 1,000.

The DVDram disks also come in double sided 9.4gig disks. And the caddies nowadays can be opened, so you can store the disks and swap them in and out of a single caddy as needed.

Also, the DVDram has a MASSIVE amount of error correction and write verification built into the disk itself, and the drive firmware. It can be used for whatever you want, but it's real purpose is corporate kind of backup and university archives.

"I personally think filesystems should be rewritten from scratch every 5 years..." --- Hans Reiser