In the past, most enterprises defined a disaster as an act of nature--a hurricane, tornado, flood or fire that wipes out their ability to conduct business as usual. Today, with worldwide networks, 24/7 customer call centers and Web applications, a common electrical failure could spell disaster when communication is interrupted in the supply chain, online transactions are halted or networks are down. Online resource Dictionary.com has even added "business failure" to the list of calamitous events that define a disaster.

With this in mind, companies are stepping up their use of hosted business continuity (BC) and availability services--not just for those acts of nature, but also for everyday occurrences that might interfere with stringent uptime requirements.

Business continuity and disaster recovery are intertwined. While disaster recovery is the set of steps and processes involved in restoring a data center to normal operation after it has been partially or totally taken offline by some event, business continuity involves managing emergency coordination, notifying employees and interacting with emergency officials.

The frequency of common business interruptions has boosted the market for external disaster recovery services--which include data center services, backup and mobile recovery services--to US$3 billion to $4 billion a year, according to Gartner.

The market size for capital expenditures on in-house servers, storage and internal staff used for business continuity and disaster recovery is harder to quantity. Very often, that server and storage infrastructure can be brought in to support other applications and initiatives. Although it still needs to be backed up and may have to be managed, restored and brought back to life, it is not always counted in the disaster recovery budget.

Here are some points to consider when evaluating business continuity and availability services and software.

1. Weigh the benefits of specialized business continuity planning software.

Business continuity planning software can help large companies formalize the BC framework and continually update the plan. "Of companies that actually have plans, 50 percent use software and 50 percent use informal software" such as Excel spreadsheets, says Stephanie Balaouras, a senior analyst at Forrester Research in Cambridge, Mass.