Suppose for a moment that a virus has infected your entire computer network. It has quickly spread through every employee's workstation, into every document and database file. All your work, all your data--it's all destroyed. How would your business recover?

Without an adequate backup and recovery plan, every business is at risk. Because companies rely on data and mission-critical applications, the cost of downtime is exorbitant, potentially exceeding thousands of dollars per hour for such expenses as recovering data and system files and replacing equipment--not to mention the loss in productivity as well as customers. According to a recent study, nearly half of the companies that are unable to fully restore their data after a disaster will go out of business entirely.

The Case for Tape

Whether backing up an individual workstation or a small network, many businesses choose tape as their storage medium because it's capable of storing high capacities of information at relatively low costs. Tape is the superior choice for disaster readiness because it is easily stored off-site, and its long, extremely stable shelf life meets archival requirements and data retention objectives that may be federally or state-mandated.

When developing a tape backup strategy, one of the considerations is the volume of data to back up. Environments with 20-800GB should consider the VXA format; for larger operations with 200-2000GB or more, LTO (Ultrium) technology is preferred by many.

Other factors to establish include the frequency of backup operations, archival goals, and tape life cycles. From this costs can be estimated for budgeting purposes and procedures can be developed to implement the backup process.

A full backup captures all data files, system files, and applications. Once the total capacity is determined, it's a simple matter to divide that number by the total capacity of each cartridge. For example, if a system's total capacity is 400GB, and each VXA tape cartridge holds 86GB, five tapes will be needed for a full backup.

Most tape drives and software applications compress data to reduce the size of the files, thus reducing the total number of tapes needed. Assume the backup will be compressed by a rate of 2:1, depending on the nature of the data and the drive and media performance. With this rate of compression, only two and a half tapes are required for the full backup.

A partial backup (incremental or differential) only copies data that is new or changed since the last full backup. This capacity requirement will vary depending on how quickly data changes, but is typically much smaller, often as much as 100 times smaller, than that of a full system backup.

The most economical tape backup strategy for SMBs is a combination of full and partial backups using the backup software's tape-append option. This will allow the writing of additional data to tape where the previous backup session left off, reducing the number of tapes needed. For even more economy, some tape formats, such as VXA, can be purchased in multiple lengths providing various data capacities depending on the individual requirements.

Stay up to Date

It's important to manage local and off-site backups to keep all tapes as current as possible. By adhering to a schedule that determines when to reuse tapes during a backup cycle, called tape rotation, the most accurate recovery possible is ensured.

A good rotation strategy defends data not only by ensuring current versions of files are always available on tape, but also by protecting the tape from excessive wear, which can lead to unrecoverable data.

There are several time-tested ways to rotate tapes simply, economically and effectively, but finding the best rotation strategy depends on the individual recovery objectives and archival requirements. Every business should develop its own tape rotation strategy to fit its unique needs. As time goes by and backup becomes second nature, you may find that your rotation schedule can be adjusted as your business needs evolve.

Retirement of tapes is based on the tape's rated service life, but if your software tracks rewrite errors, any tape that shows a significant increase in errors may indicate that it should be replaced.

Here are some more tips:

* Eliminate manual operations. A tape autoloader is a tape drive, plus a mechanized carousel that moves tape cartridges, in a single secure enclosure. Autoloaders eliminate the need for a person to insert and remove tapes, and can provide about two weeks of unattended backups. Dramatic reductions in prices mean autoloaders are now available for around the price of a single tape drive.

* Perform backups without exception. If employees are responsible for backing up their own data, backups won't always happen. Centralize the backup process across a network and consider using backup software that performs the process automatically.

* Verify that the backup was completed successfully. Most software has a verification feature, and it's a good idea to run through a practice restore of one or two unimportant files to be sure the backup is valid.

* Rotate tapes to preserve multiple copies of data. Don't reuse the same tape for backup every day. If that tape is lost of destroyed, the data will need to be recreated file by file. Also, create alternate copies of your data in case a tape is damaged.

* Keep backup tapes both at the company site and at an alternate location. In the event of a day-to-day disaster (for example, a file gets accidentally deleted or a local hard drive dies), keep a set of backup tapes on site for quick recovery. In the event of a major disaster that affects your company location (such as fire or flood), keep a set of backup tapes off-site in a secure location so business can be restored to normal operations.

* Use antivirus software. Protecting the computer system itself prevents viruses from being transferred onto backup tapes.

* Clearly label tape cartridges for quick identification. Label each tape with the date of backup, type of drive used, and enough information to identify the contents. For example: "3/24/06 VXA: Personnel Weekly Full Backup."

* Take proper care of the tapes. Store tapes according to the recommendations listed on the tape packaging. Do not expose tapes to sources of contamination, like copiers and printers that emit toner and paper dust.

* Take proper care of the tape drive. Most drives require periodic cleaning with a separate cleaning cartridge. Follow the manufacturer's cleaning recommendations.

* Consider using an archive vendor for tape storage. An archive vendor can provide services ranging from secure facilities for tape storage to prepaid delivery of your tapes in the event of a disaster.

Kelly Beavers is vice president, product marketing at Exabyte.

Tape vs. disk backup: Which one to pick?

In the world of backup technology, the debate still rages: Which is better, tape or disk-based? Here are some pros and cons of each approach.

Disk-based pros:

* Flexibility: Snapshots log block level changes that can be reassembled with replicas. This provides instantaneous file restores and image rollbacks of entire volumes

* Performance: Snapshots typically take only seconds to perform, meaning they can be performed frequently and even continuously

Disk-based cons:

* Cascading corruption: Data corruption, virus infection, or other aberrations permeate subsequent snapshots, which can potentially affect the entire data protection set

* Short term: Space constraints limit number and size of snapshots, reducing effectiveness for long-term data protection

* Poor portability: Images are usually bound to the array or device that created them, which limits the portability or migration of protected data

* Application impact: The frequent access of volumes competes with application access, which can affect application performance

Tape backup pros:

* Cost: Tape media are significantly less expensive for large capacities than disk drives and their operation costs are generally lower

* Portability: Tape media can easily be moved and taken off-site for storage and disaster protection.

Tape backup cons:

* Mechanical complexity: Tape drives and tape media are complex and fragile, and fail more often than disk drive mechanisms

* Serial access/linear format: Tape media are written serially with data laid out linearly on the tape and don't efficiently support random-access or block level access.-- Keith Mansfield