Most people with a computer want to preserve their data at some point. Saving to a hard drive is fine, but if it becomes damaged, retrieving your data could be impossible. Moreover, when it comes to music and movies, you might want to listen or watch them away from your PC. This page explains types of media storage that drives use as well as the drives themselves.
Discs:
A CD (compact disc) stores data or audio, the audio which can be played in a regular CD player in your home or car. There are two types of discs for recording: CD-R (CD Recordable), which are the most popular, and CD-RW (CD Rewritable). Recordable dics can be written to only once. The content is permanently stored. Rewritable discs can be erased and rewritten to repeatedly. CDs store up to 700 MB of data or 80 min of audio.
DVD stands for Digital Versatile Disc (or Video Disc). Its primary function is to store video, but just as easily records other data. Like Cds, they are either recordable or rewritable, but store a tremendous amount of data. The various formats and they're capacities are on the next page.
Formats:
These are the standard DVD media formats:
- DVD+R (plus R) and DVD-R (dash R) - These two are the record once formats.
- DVD+RW and DVD-RW - These are the rewritable formats and can be rewritten over 1000 times.
DVDs have various storage capacities. They're determined by the number of layers a disc has and whether or not it can be written to one or both sides. The original and still very popular is the single-sided, single layer (DVD-5). Data is written to one side only. These hold 4.7 GB of data or 2 hrs. of video. Supported by DVD+/-R and DVD +/-RW formats. Other DVD sizes are listed below.
- Double-Sided Single Layer (DVD-10): Data can be written to both sides-like a cassette tape. Stores 8.75 GB or about 4.5 hrs of video. Also supported by DVD+/-R and DVD +/-RW.
- Single-Sided Dual Layer (DVD-9): Records to one side but that one side has two layers built into it. Stores 8.5 GB of data or 4 hrs. of video. Supported by DVD+R and DVD-R. They are normally termed DVD+R DL and DVD-R DL.
- Double-Sided Double Layer (DVD-18): Stores 15.9 GB of data or over 8 hrs. of video.
DVD-RAM:
DVD-RAM discs can be rewritten over 100,000 times and are either single-sided or double-sided - single-sided having a capacity of 4.7 GB and double-sided a capacity of 9.4 GB. Unlike the aforementioned formats, DVD-RAM does not require burning software-they function like hard drives and are available with or without a cartridge. However, they are not as compatible as the other types and are a bit more expensive.
Blu-Ray (BD):
Blu-Ray (BD) is the latest video disc. It gets its name from a blue laser used when recording to and reading a disc. All the other DVD formats utilize a red laser. This blue laser has a shorter wavelength, thus allowing the storage of extremely large amounts of data. Blu-ray is primarily for high-definition content and comes in single and dual layer. Single layer discs store up to 25 GB - that's 2 hrs. of hi-def content or 13 hrs. of standard video. Dual layer stores 50 GB, which is 4.5 hrs of hi def video or 20 hrs of regular video.
Drives:
Now that we have discussed the various media types, let's look at the optical drives themselves. Optical disc drives store data on a flat disc using a laser. CD and DVD writers (a.k.a. CD/DVD burners) are two examples of these types of drives and allow you to make your own data, music, or video disc. This process is referred to as "burning a disc". These drives can be installed internally or externally. Since DVD burners can also record and play CDs, CD writers are now practically obsolete.
Optical disc drives come in different speeds that measure how fast they write, rewrite, and read data. Listed first is usually the write speed, followed by the rewrite and read speeds. These three rates are written with an "x" separating them (for instance, 32 x 12 x 48) and are based upon the original 1x record speed of the first CD or DVD writers. The first CD writers recorded at 150 KB/s (1 x 150), therefore every rate afterwards is a multiple of that speed.
Using the numbers above as an example, lets say a CD drive is advertised as 32 x 12 x 48. The maximum record speed for writing a CD would be 32 times the original rate, in other words, 32 times 150 KB/s. The rewrite speed 12 times 150 KB/s, and the read speed 48 times 150 KB/s.
DVD burn speeds work the same way, except the original DVD writer speed was 1.32 MB/s. Also, since there are several types of DVD discs (+R,+RW, -R DL, etc.), you may first see all the write speeds listed for these various formats before seeing their re-write and read speeds. Since DVD burners record and play CDs as well, you'll most likely see the DVD rates for these too.
