The Ultimate Buyer's Guide to HA/DR Solutions

Due to globalization, Web-based sales and service, more vigorous competition, and more stringent regulations, the goal of ensuring the availability and recoverability of data and applications has risen considerably on the priority lists of today’s CIOs. A wide range of technologies is available to address this goal. At the apex of a spectrum of solutions sits a strategy that maintains highly redundant, geographically dispersed systems and data, commonly identified as High Availability (HA) or Disaster Recovery (DR). Occupying the lower extreme is traditional tape-based backups, which provide reliable but rudimentary disaster recovery capabilities. But between the two sit a variety of technologies offering various levels of system availability and recovery speed and completeness.

Depicting this continuum along a single line from low-end disaster recovery to high-end high availability would be misleading. HA and DR are not mutually exclusive. Both may be required to provide complete protection. For example, a tape-based DR solution cannot be used as a means to keep systems available during brief outages, such as those required by normal maintenance. At the same time, an HA solution may be of no help in recovering from a wide-area disaster such as an earthquake, because both the production and HA backup system may be destroyed, even if they are placed in separate buildings in the same city.

The point is that to understand the HA/DR solutions spectrum requires two-factor analysis. Each technology must be considered for both its ability to protect data and its ability to keep operations online or bring them back online quickly. Each class of technology in the HA/DR spectrum exhibits different operating characteristics and provides a fairly distinct range of data protection and downtime avoidance. Indeed, the capabilities of some technologies can overlap each other. Other solutions are focused on a single specific technical issue, such as a disk drive failure.