In most businesses, the information stored on computers is irreplaceable. Customer databases, tax records, marketing materials, and intellectual property may all be stored on computers throughout the office. But every year thousands of companies lose computer data because of fires, floods or burglaries. Many more experience smaller losses from system crashes, accidental erasures or computer viruses. If one of these has never happened to your firm, you can consider yourself very lucky indeed.

Computer backup systems help businesses avoid these catastrophes by providing a safe way to maintain important files. They are designed to protect against both system failures and business catastrophes. By storing copies of data outside the office, you can keep your files safe at all times.

This guide is designed to give you the facts you need to purchase a computer backup system for your business. The various sections are listed in the box above. You can choose to read this guide from beginning to end, or jump directly to a section of interest.

There are two basic ways to back up computer data:

Removable Backup Tape
The most common method of backup is to record a copy of your data onto some type of removable tape. This can vary from a simple floppy disk to high-tech removable cartridges and tapes. These should be taken off-site each day, so a recent copy of your files can be accessible outside the office in the event of a disaster.

Network Connections
In this case, a firm sends a copy of files to a remote system via a phone line or Internet connection. The information is thus guaranteed to be stored off-site.

For most firms, tape drives are the best choice for completely backing up a computer system. Economical at less than a cent per MB, tape can handle up to 40 GB of data on a single reel, and tape drives can write data at very high speeds.

The biggest drawback with tape is that the data is not easily accessible. While you will find tape to be a lifesaver if your hard drive is wiped out, it is often very frustrating trying to locate one lost file. But because of their low cost and high storage capacities, most firms use backup tape for at least a portion of their backup strategy.

There are three types of backup tape:

Quarter Inch Cartridges (QIC)
QICs are one of the oldest tape drive standards in the industry. While older QIC formats hold only a few hundred megabytes (MB) of data, the newer Travan QIC format can hold up to 2 gigabytes (GB) of uncompressed data. Unfortunately, these drives can be noisy.

Digital Audio Tape (DAT)
These are designed for companies with somewhat larger backup needs. Using a 4 mm tape originally designed for digital audio players, DAT drives can handle 1 to 4 GB per cartridge. These drives are especially well suited for businesses that need to back up numerous small files.

Digital Linear Tape (DLT)
DLT drives emerged from mainframe storage systems, and are typically used in very large backup systems. DLT drives tend to start at about $2,000, but can store 20 GB or more.

Floppy Disk
This is the least expensive type of removable backup, since all computers are equipped with a disk drive. Unfortunately, floppy disks do not hold enough information to easily back up most modern computers.

Removable Cartridges
Most new cartridge drives, such as SyQuest or Iomega Zip or Jaz drives, hold at least 1 GB of data, making them quite adequate for backing up individual computers. They also can access data very quickly, simplifying data retrieval. On the downside, cartridges tend to be fairly expensive, making the drives impractical for backing up many gigabytes of data.

Optical Drive
Optical or magneto-optical drives record on removable disks that hold anywhere from 650 MB to several GB of data. The fastest growing type of optical storage is the recordable CD drive, or CD-R, which allows you to record data onto a disc that can be played in any CD-ROM player. With CDs going for under $2, CD-R technology is an inexpensive and convenient form of backup. Re-writable drives, or CD-RWs, allow updating and deleting of files as needed. A re-writable CD goes for around $12. But since you can reuse a CD-RW disc several times, it will be less costly in the long run.

Most tape drives come equipped with software that allows unattended backups of a single computer or a small network. For larger networks, you generally have to buy third party software that works with the backup drive and the network operating system.

Software must be able to handle problems during backup and recovery. It should allow recoveries to be made from any individual tape or disk, and should be tolerant of user mistakes, such as files that are left open, by alerting the user rather than crashing or aborting the backup.

Test the Equipment
Some businesses have backups that seem to go as planned for months, only to discover when an emergency arises that no data was in fact recorded.

Parallel Problems
Avoid systems with a parallel printer port connection. These transfer data much more slowly than devices using a SCSI or IDE connection.

Clean It Up
Tape drives require frequent cleaning to remain in working condition. Buy a tape head cleaner to prolong the life of the head, and set a schedule for cleaning the drive.

Silver Watch Rule
Tapes that are frequently used should be retired after about one year.

Store Off-site
Businesses should use a backup routine that keeps at least one complete set of data off-site at all times. In many cases, the best approach is a grandfather-father-son approach, which records three complete versions of all data. If a backup does not go as planned, this means there are still two recent copies of the data available