Linux – High level command line program for burning CDs and DVDs

Probably preaching to the choir here, but this is experience gained after a couple decades of using the darn things. My first drive was a really expensive SCSI interface 1x CD-R. That $250 you pay for a really good manufacturer now? Pfft! I could buy six now for what I paid for that thing. Ouch!

1. Use a quality drive to produce the disk
2. Use a quality disk manufacturer (Mitsubishi, JVC, Sony) and as fresh a batch of disks as you can get.
3. Make sure the disk surface is clean before inserting into the drive
4. Slower burn speed is supposed to produce larger dots, verify data after burn
5. Multiple copies of important data is a "Really Good Idea™"

Also:

1. Time will degrade the write-ability of the dye layer, slow burn speeds will not make up for this, use as fresh a disk as you can get.
2. Heat will degrade the dye used in the writable layer.
3. Ultraviolet light will degrade the dye used in the writable layer.
4. Moisture can get through the label side coating and attack the aluminum flash layer.
5. In certain environments, there is a sort of mold that will eat the label side of the disk, even on pressed disks.

The 20-30 year lifespan quoted for writable disk life was based on advanced aging tests, not real lifetime tests. Real life shows that a high proportion of written disks probably aren't much good after 10 years.

So the name of the game is "make multiple copies over several media types for long term storage" on rather static data. With multiple copies, there's a chance of recovery of the bad files.

The case is not so good if large databases are involved, a couple bad spots can render the whole database useless on a couple disks. Most backups have a lifetime of weeks, so this isn't as much of an issue, but for monthly backups, you may need to do refresh copies every so often if long term storage is a legal liability.

Why do CDs and DVDs fill up their data from the middle outwards?

Note the above assumption made in the question is incorrect.

Summary:

• For historical reasons writing (and reading) from the inside makes sense (different size disks are possible as explained in other answers).

• For read performance reasons modern disks may be written (and read) outside in or even in both directions (dual layer).

Notes:

1. Most disks are a standard size.

2. Commercially produced CDs and DVDs are not written but stamped on a press.

   Although all DVDs (both homemade and commercial) utilize "pits" and "bumps" physically created (the pits on the unreadable side, and the bumps are on the readable side) on the discs to store the video and audio information, there is a difference on how the "pits" and "bumps" are created on commercial DVDs vs the way they are made on a home recorded DVD.

   DVD movies you buy at the local video outlet are manufactured with a stamping process. This process is sort of like the way vinyl records are made - although the technology is obviously different (vinyl records are stamped with grooves versus DVD being stamped with pits and bumps).

   Source The Difference Between Commercial and Home-recorded DVDs

The rest of this answer concentrates on the performance aspect.

The exceptions to writing (and reading) from the inside are XBox games (and other games consoles games) and Dual Layer DVDs (movies).

Xbox Games

Xbox games have the data written from the outside in for performance reasons - since the outside is spinning faster than the inside the data can be read faster.

The Xbox games themselves are stored on DVD-9 (9GB single sided, double layer) formatted discs and are actually written in a very interesting fashion. The games are written from the outside of the DVD-9 discs to the inside, meaning that most discs will actually have the majority of their data stored around the outer perimeter of the disc.

Since the DVD drive in the Xbox is a Constant Angular Velocity (CAV) drive, it can read more data per second off of the outermost tracks making this a highly optimized way of storing data on the DVDs to reduce load times. Obviously the drive can also read regular CDs and DVDs as well.

Source Hardware Behind the Consoles - Part I: Microsoft's Xbox

Dual Layer DVDs (Movies)

Dual Layers DVDs can be written in either direction - there are two write modes.

Most movies are written as opposite track path. A movie will be split across across the layers, so no seek back to the inner edge is needed at the layer change.

There are two modes for dual layer orientation. With parallel track path (PTP), used on DVD-ROM, both layers start at the inside diameter (ID) and end at the outside diameter (OD) with the lead-out. With Opposite Track Path (OTP), used on DVD-Video, the lower layer starts at the ID and the upper layer starts at the OD, where the other layer ends, they share one lead-in and one lead-out.

Source DVD-R DL