Choosing adequate media

Every system and every environment requires different considerations when choosing a medium on which to back up its data. A person with a single computer has different needs than a company with several machines containing mission-critical data. Therefore, choosing how to back up these systems involves considering your needs.

Several forms of backup media are commonly used. Table 18-1 lists and compares the more commons forms of backup media. Following the table, I explain each medium type in more detail.

Table 18-1 Comparison of backup media




Hardware cost

Medium cost



Medium to fast













Hard drive



















The magnetic data storage tape is one of the computer industry's leading forms of backup media. The drives used for the tape backups may be a little more expensive than other devices, but the media used with the drive more than makes up for that expense. Tape drives and the corresponding media come in all styles, forms, and sizes. Most SCSI tape drives work with Linux, and many of the IDE versions are compatible as well with "SCSI emulation" turned on for the kernel.

Another attractive quality of tapes is their data-holding capacity. In a very small space, they can hold many gigabytes of data. For small systems, this may not be a concern; but for large sites, it can make all the difference in the world.

Tapes are also very well accepted as a backup medium with software supporting the devices. Much of the early software supports tape drives, so finding appropriate software to fit your needs is easy.

The tape media lends itself to making complete backups, backing up and restoring large chunks of data quickly. Each time you add data to a tape, it is added to the end of what you wrote last. Recovering files, on the other hand, is a long, arduous process that takes a lot of time when you do one file at a time. Because files are placed on the tape in sequential order, recovering random files can be a major drawback. The more frequently you perform a single file restore, the less desirable this medium looks.


CD-ROMs are very affordable forms of backup media. The disks are cheap, and they hold enough data for most systems. The two forms of CDs are writeable and rewrite-able. Both are limited to the amount of data they hold; however, the rewritable CD-ROM is reusable, which extends its life tremendously.

For smaller systems and individuals that wish to save only their vital data, CD-ROMs are an excellent choice. The media isn't very expensive as long as you don't have to make frequent backups. Software is also available specifically for doing backups on CD.

Restoring files from a CD-ROM is much quicker than tape because of its capability to randomly access files. In this case, a CD makes a great medium to back up frequently changing data such as document drafts, log histories from manufacturing equipment, and source code from programming projects in which making fast restores is important.

The major downfall with this medium is its low capacity. CD-ROMs only hold approximately 650MB. This, compared with some of the other options such as a hard drive, is very small.

Hard drive

As long as your equipment can hold an extra hard drive or two, invest in hard drives because they are fast and relatively inexpensive and they hold several gigabytes of data. This is the best choice when working with a mission-critical system. Hard drives are good when you can't afford to wait hours for a repair, restore, or rebuild of a system. Minutes of down time can cost you tons of money in lost sales revenue or data.

Hard drives can be removable in some manner, which enables you to replace the drives. Therefore, using hard drives increases the number of historical backup revisions. Non-removable drives fixed inside the case of a computer run the risk of losing all the data if something destroys the entire computer, as with a fire.

For data that you need to back up frequently throughout the day, the hard drive can serve you well. Using a hard drive increases the chances of the most recent data recovery. For very critical and not so critical environments where frequent backups and fast recovery are important, use RAID.

Tip As you look through the various forms of media, remember that you can also use a combination of backup media. For instance, use a hard drive mirror to provide ' the immediate recovery, and use tapes to provide the historical archive of backups. Combination methods can give you the best of both worlds.

Other media

There are several other forms of media to use as backup: high-density floppies, Iomega Zip and Jaz, and so on. You can use anything that holds data as backup media; the only hindrance is the hardware's capability to work with Linux. As long as the hardware can work with Linux, you can use its media.

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