Unix Backup and Recovery

The Impact of an HA Solution

With a proper HA solution in place, you will know when something goes wrong, and the system will try to react to that without human intervention. Once something does go wrong though, the purpose of the HA software is not to allow you to ignore the problem but rather to maintain stability long enough to give you a chance to diagnose the problem and fix it. Remember, an HA environment coupled with a volume management package is a complement to your normal backups, not a substitute.

What Are the Pros and Cons of HA?

HA is a great answer for mission-critical applications and environments that require close to 100 percent uptime. Properly configured and administered, an HA solution can be valuable to solve even disaster recovery situations in a timely manner.

On the negative side, a particular HA system may not provide the necessary solution for a particular application. As far as I know, there is no HA implementation that can perform application migration and duplicate an application state at failure time. If such a feature is an absolute requirement, it may be necessary to turn to fault-tolerant systems, which are briefly introduced in an earlier section.

Cost also may be a concern. HA packages are pricey and may not necessarily target a particular environment properly. Remember, HA requires a functional duplicate of your primary server, plus additional hardware and software to complete the equation. Study your options carefully and completely before making ...