Removable Media

Since the mid-1980s, the primary storage device used by computers has been the hard disk drive. However, for software loading, data backup, data transport between computers, and temporary storage, removable media storage devices such as optical drives, magneto-optical drives, magnetic disk drives, tape drives, and flash memory devices are useful supplements to primary storage. These types of drives can be used as a supplement to hard disk storage as well as for primary storage.

The options for purchasing removable devices vary. Some removable-media drives use media as small as a quarter of your index finger, whereas others use larger media, up to 5 1/4''. Most popular removable-storage drives today have capacities that range from as little as 16MB to as much as 100GB or more. These drives offer fairly speedy performance and the capability to store anything from a few data files or less frequently used programs to complete hard disk images on a removable disk or tape.

Three main types of technology are available for removable storage on laptop PCs (or desktops):

• Magnetic disk

• Optical disc

• Flash (ROM)

Magnetic disks include floppy drives, Zip drives, LS-120/240 SuperDisk drives, and external hard drives. Optical discs include CD/DVD-ROM, CD-RW, and DVD+-RW. Flash memory includes CompactFlash, Secure Digital, MultiMediaCard, Smart Media, and more. This chapter examines these three main classes of removable storage.

Apart from hard disk drives, laptop systems can use many other types of storage media that can provide access to larger amounts of data. CD-ROM drives have been standard in laptop systems for many years now, with most of the newer systems offering CD-RW, DVD-ROM, and even combo DVD/CD-RW drives. Some of the latest systems are starting to offer DVD+/-RW drives as well. As accessories, some systems also offer removable high-capacity floppy or cartridge drives, such as the LS-120, LS-240, or Iomega's Zip drive. This has been made possible by the enhanced IDE specifications that let other types of devices share the same interface as the hard drive.

Another important issue is the floppy drive. Many systems now omit the floppy drive to save space, either offering an external drive connected via USB or one that can work in a drive bay interchangeably with other devices, such as optical drives. Depending on the type of user , the lack of a floppy drive might or might not be an acceptable inconvenience. Many users of portables, especially those who frequently connect to networks, have little use for a floppy drive. This is now true even for the installation of applications because virtually all software now ships on CD-ROMs.

One of the features that is becoming increasingly common in laptop systems are modular drive bays that are capable of supporting several types of interchangeable components . Most systems with modular bays offer multiple devices for these bays, including a floppy drive, several types of optical drives, hard drives, and secondary batteries. This arrangement lets you customize the configuration of your system to suit your immediate needs. For example, when traveling you might remove the CD/DVD-ROM drive and replace it with an extra battery or a second hard drive.

Laptop vendors and magazine reviews might refer to the number of spindles when discussing the number of drives a laptop can have installed simultaneously . Nearly all laptop systems can be classified as one-, two-, or three-spindle systems. One-spindle systems are the smallest and lightest, incorporating only a single internal hard disk, and no other internal drives. Other drives, such as floppy or CD/DVD drives, must be connected externally (via USB in most cases) or via some type of docking station. The ThinkPad X31 series from IBM is an example of a one-spindle system.

Most laptops are two-spindle systems. If a system has two spindles, the most common configuration is an internal hard drive along with a modular bay supporting several interchangeable devices including a floppy drive, several types of CD or DVD drives, a battery, a second hard drive, and possibly other items as well.

A three-spindle system normally includes an internal hard drive, a floppy drive, and a single modular bay, or possibly an internal hard drive and two modular bays. These are sometimes called all-in-one systems , referring to the fact that a floppy, hard disk, and optical drive can be mounted in the system simultaneously. With the elimination of the floppy drive from most newer laptops, three-spindle systems are becoming rare. When evaluating your laptop needs and hardware, be sure to determine which devices included with a model can be used simultaneously and which require removing another device.

Tip

If a particular laptop is described as a one-spindle or two-spindle system, you should determine which drive(s) has been omitted and decide whether it's acceptable to use an external drive as a substitute. Many two-spindle systems use an internal hard disk and one modular bay drive. This means that if you want to use a floppy drive, you'll have to either carry an external USB floppy drive, or swap a modular bay floppy drive for the optical drive, which means the floppy and optical drives cannot be used simultaneously.

If lightweight travel is a concern, determine which parts you don't need for travel that can be swapped out. Modular bays can sometimes be equipped with a "weight-saving module," which is a dummy drive for the open bay to prevent dirt and foreign objects from entering when the bay is empty. If a particular system doesn't include a dummy drive, one may be available as an option.

If you aren't satisfied with the removable modular bay drives your current laptop offers, the PC Card slots and USB or FireWire connectors are your gateway to virtually unlimited choices in external drives. All the popular desktop choices, such as CD-RW drives, DVD+-RW drives, high-capacity hard drives, tape backup drives, floppy drives, and Zip or LS-120 SuperDisk drives, can be attached via USB, FireWire, or SCSI interfaces. If these interfaces are not built in (most systems have USB, many also have FireWire, but few if any have SCSI), they can be added via PC Card or CardBus adapters.

In most cases, external drives should be interfaced via high-speed USB 2.0 or FireWire, because those are among the highest performance and most popular interfaces. In the past, external drives were available in parallel port versions. Although parallel port drives were popular at one time, many newer laptops lack legacy serial and parallel ports, and you'll normally suffer a big speed drop for large file transfers, especially if you don't use the high-speed EPP/ECP IEEE 1284 LPT port modes. Instead of the parallel port, you should consider using your system's USB or FireWire ports.

You can transfer files between two systems by directly connecting them together via their Ethernet ports, parallel ports, or even USB ports. Note that special cables are required for these connections. LPT.com, the originator of the Direct Cable Connection program provided with Windows, is a popular source for these cables and setup help.

Interfaces for Removable Media Drives

In addition to choosing a type of device, you need to choose which type of interface is ideally suited for connecting it to your system. Several connection options are available for the leading removable drives. The most common interface for internally mounted drives is the same ATA (AT Attachment) interface used for most hard drives. SCSI interfacing is as fast or even faster for use with external drives, however SCSI devices are expensive and require the addition of a PC Card that provides a SCSI interface. It should be noted that high-end tape backups like DAT often require a SCSI interface.

FireWire (IEEE 1394/i.LINK) is commonly used for connecting video cameras and high-capacity external hard drives.

However, the most commonly used external interface is now the USB port, which is replacing legacy ports such as the venerable parallel port for printing as well as interfacing external drives and other types of I/O devices. The USB port is available on virtually all recent PCs (both desktop and laptop models); it can be hot-swapped, and it's supported by Windows 98 and later versions, including Windows Me, Windows 2000, and Windows XP. Older interfaces, such as the parallel port and PC Card (for laptop computers), are still used on some devices but have limited performance. These are recommended only for systems that don't support USB 2.0 Hi-Speed operation (such as those with USB 1.1 ports or those still running Windows 95 or Windows NT). Some external removable-media drives allow you to interchange interfaces to enable a single drive to work with a variety of systems.

Note

Although late versions of Windows 95 ("Win95C" or OSR2.1 and above) also have USB drivers, many developers of USB devices do not support their use with Windows 95. For reliable results and manufacturer support, use Windows 98, Windows Me, Windows 2000, or Windows XP.

As you will see in the following sections, most removable-media drives are available in two or more of these interface types, allowing you to choose the best interface option for your needs.

Note

Connecting or installing removable-media drives is similar to connecting and installing other internal and external peripherals. The external USB, FireWire (IEEE 1394/i.LINK), and parallel port drives are the simplest of the available interfaces, requiring only a special cable that comes with the drive and the installation of special software drivers. See the instructions that come with each drive type for the specifics of its installation.

See Chapter 8, "Expansion Buses," and Chapter 9, "Hard Disk Storage," for details on how these interfaces operate .

Removable Magnetic Disk and Optical Disc Storage

Computers have basically two types of disk/disc storage: magnetic and optical. Magnetic storage is represented by the standard floppy and hard disks that are installed in most 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 it 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 or SuperDisk floppy drive) or a laser to heat the disk so it can be written to magnetically, thus polarizing areas of the track, which can then be read by a lower- powered laser, as in magneto-optical (MO) drives.

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 in the near future 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. In fact, some would say that has already happened . Most new systems today include a CD-RW drive as a minimum, and many systems no longer include a floppy drive. Even if a floppy drive is included, it is rarely used except for running tests, running diagnostics, or doing basic system maintenance, disk formatting, preparation for OS installation, or configuration.

The next series of sections in this chapter investigate the popular and standard forms of removable storage used with modern laptop systems.

Backing Up Your Data

Any computer book worth reading warns repeatedly that you should back up your system regularly. Backups are necessary because at any time a major problem, or even some minor ones, can corrupt the important information and programs stored on your computer's hard disk drive, rendering this information useless. A wide range of problems can cause a loss of the data on your hard drive. Here is a list of some of these data- damaging problems:

• Sudden fluctuations (power spikes) in the electricity that powers your computer, resulting in data damage or corruption.

• Overwriting a file by mistake.

• Mistakenly formatting your hard disk when you meant to format a floppy or other type of removable media.

• Hard drive failure resulting in loss of data that has not been backed up. Not only do you have to install a new drive, but, because you have no backup, you also must reinstall all your software.

• Catastrophic damage or complete loss of your computer ( storm , flood, lightning strike, fire, theft, and so on). A single lightning strike near your office or home can destroy the circuitry of your computer, including your hard drive. Theft of your computer, of course, is equally devastating, and especially problematic for laptop systems, since they are so easily moved. A recent, complete backup greatly simplifies the process of setting up a replacement computer.

• Loss of valuable data due to a computer- related virus. One single download or floppy disk can contain a virus that can damage valuable files and even your entire hard disk. With several hundred new viruses appearing each month, no antivirus software program can keep you entirely safe. A recent backup of uninfected, critical files can help repair even the worst damage.

Backups are also the cure for such common headaches as a full hard drive and the need to transfer data between computers. By backing up data you rarely use and deleting the original data from your hard drive, you free up space once occupied by that data. If you later need a particular data file, you can retrieve that file from your backup. You also can more easily share large amounts of data between computers ”when you send data from one city to another, for example ”by backing up the data to a tape or other media and then sending the media.

Regardless of how important regular backups are, many people avoid making them. A major reason for this lapse is that for many people, backing up their systems is tedious work when they have to use floppy disks or other low-capacity media. When you use these media, you might have to insert and remove many disks to back up all the important programs and data.

Optical storage, high-capacity magnetic media, and tapes are all useful devices for making backups. Historically, tape backups have been regarded as the most powerful of these technologies because they are among the few backup devices capable of recording the contents of today's multigigabyte drives to a single cartridge for restoration.