Keys to Data Storage

You can store data in a variety of formats. The format you choose depends on your needs. Some factors to consider when choosing media, or types of storage devices, are:

• Should the media be fixed or removable? Fixed media stays with the computer and offers the best performance. Removable media adds the benefits of being mobile for use with another computer or for backup purposes but is slower.

backup

The copying of all your data to a secondary storage option. If your primary storage option becomes unavailable, you can use backups to restore the operating system, application, and data files.

• What capacity do you need now and in the future? Are you storing a small amount of data or a large amount of data?

• How common is the storage media? If the storage media is not commonly used, it might be incompatible with other computer types. For example, if you received a 51⁄4-inch floppy disk, would it work on your computer? Would it work on most computers that are sold today?

• What is the cost of the storage media? Cost is often a primary concern and is measured in cost per megabyte. When read/write compact discs (CDs) first became available, most users considered them to be too expensive. Because prices have dropped so significantly, CDs are now a common storage media.

Here are some storage quantities and their equivalents:

1,024 kilobytes (KB)	= 1 megabyte (MB)
1,024MB	= 1 gigabyte (GB)
1,024GB	= 1 terabyte (TB)
1,024TB	= 1 petabyte (PB)
1,024PB	= 1 exabyte (EB)

Note 

When specifying the amount of storage you need, keep in mind that a well-built system should also have a reliable backup solution. (We discuss tape backup in the section 'Tape Drives,' later in this chapter.) The key point to remember is that if you are going to need 25GB of hard drive storage, you will need an equivalent amount of storage space on something easily transportable-in this case, a tape-to copy your data.

PC card

A small, thin device the size of a credit card. PC cards follow the PCMCIA (Personal Computer Memory Card International Association) standard and can be of three types. Type 1 supports RAM or ROM expansions for mobile computing devices. Type 2 is slightly thicker to accommodate modems and network cards. Type 3 is the thickest and is designed for mobile storage.

Here is a summary of the most common storage media.

Media	Description	Fixed or Removable	Data Capacity
Hard drive	Storage device that stores large amounts of data. Uses a series of magnetically coated disks to store ones and zeros.	Usually fixed, but some are removable	New drives are in the gigabyte range.
Floppy disk	A removable plastic disk that stores small amounts of data. This is a popular media because of its low cost and wide availability.	Removable	Standard 31⁄2-inch floppy disks can hold 1.44MB of data.
Removable disk	Removable disks come in several formats. Most removable disks have platters similar to hard drives. Models designed for mobile users have PC cards.	Removable	40MB for PC cards to 2GB for removable disks.
Compact disc	CDs are optical discs that store data by using lasers. Traditional CDs (CD-R) can be written to one time but read many times. Rewritable CDs (CD-RW) can be written to several times.	Removable	CDs hold about 650MB of data.
Digital video disc	DVDs are a new type of optical disc that have a storage capacity many times that of CDs.	Removable	A single-sided DVD can hold 4GB of data. A double-sided version can hold more than 8GB of data.
Tape	Tape is a magnetic media that you commonly use for backup purposes. It is a slow media for accessing data, but its large capacity and low cost make it ideal for backup.	Removable	Tapes can range from 250MB to 100GB.