Hardware Reference
In-Depth Information
and DVD-RW. These are two different and competing technologies for how the data is
written to the disc. Most drives can write in either format.
Some non-computer DVD players, especially older ones, may reject one
format or the other, so you may want to test your DVD player to make sure
it can read movies written to a certain type of DVD disc before investing in
a large quantity of blanks.
Blu-Ray Disk Drives
Blu-ray discs (BD)
are physically similar to DVDs but hold more data, so they're suitable for
high-defi nition movies and high-volume data storage. A BD can hold 25 GB per layer and can
have up to two layers for a total of 50 GB. Table 2.6 summarizes Blu-ray storage capacities.
TABLE 2.6
Blu-ray storage capacity
Size
Number of Layers
Capacity (Gigabytes)
8 cm
1
7.8
8 cm
2
15.6
12 cm
1
25
12 cm
2
50
Blu-ray technology uses blue light lasers instead of the red ones used for CD and DVD
reading and writing. (Drives that support all of those standards have two separate lasers.)
The laws of physics behind the shorter wavelength of blue light allow for at least 10 times
more data to be stored on a Blu-ray disc than on a DVD. Depending on the speed of the
drive, data throughput can range from 36 to 432 Mbps, as outlined in Table 2.7.
TABLE 2.7
Blu-ray speeds
Speed
Data Rate (Megabits per Second)
1x
36
2x
72
4x
144
8x
288
12x
432
