Upgrading and Repairing PCs

Chapter 13. Optical Storage

There are basically two types of disk storage for computers: magnetic and optical. Magnetic storage is represented by the standard floppy and hard disks installed in most PC systems, where the data is recorded magnetically on rotating disks. Optical disc storage is similar to magnetic disk storage in basic operation, but it reads and records using light (optically) instead of magnetism. Although most magnetic disk storage is fully read- and write-capable many times over, many optical storage media are either read-only or write-once. Note the convention in which we refer to magnetic as disk and optical as disc. This is not a law or rule but seems to be followed by most in the industry.

Some media combine magnetic and optical techniques, using either an optical guidance system (called a laser servo) to position a magnetic read/write head (as in the LS-120/LS-240 SuperDisk floppy drive) or a laser to heat the disk so it can be written magnetically thus polarizing areas of the track, which can then be read by a lower-powered laser, as in magneto-optical (MO) drives. These technologies are covered in Chapter 12, "High-Capacity Removable Storage."

At one time, it was thought that optical storage would replace magnetic as the primary online storage medium. However, optical storage has proven to be much slower and far less dense than magnetic storage and is much more adaptable to removable-media designs. As such, optical storage is more often used for backup or archival storage purposes and as a mechanism by which programs or data can be loaded onto magnetic drives. Magnetic storage, being significantly faster and capable of holding much more information than optical media in the same amount of space, is more suited for direct online storage and most likely won't be replaced in that role by optical storage anytime soon.

The most promising development in the optical area is that CD-RW (compact disc-rewritable) or DVD+RW (DVD+rewritable) drives with EasyWrite (Mount Rainier) support are starting to replace the venerable floppy disk as the de facto standard, interchangeable, transportable drive and media of choice for PCs. In fact, some would say that has already happened. Most new systems today include a CD-RW drive, and some also include some type of rewritable DVD drive. Even though a floppy drive is also included with most systems, it is rarely used except for running tests; running diagnostics; or doing basic system maintenance, disk formatting, preparation for OS installation, or configuration.

This chapter investigates the popular and standard forms of optical storage found in modern PCs.