August 1999
READERS' BEST TIPS
Buying Reliable Systems:
When is High Availability Worthwhile?
Decisions to purchase High-Availability (HA) systems can be justified financially in terms of down time. Down time can be quantified as how many dollars per hour a company will lose if their primary system goes down, multiplied by the number of average downtime hours per event. Companies should go through an extensive down time analysis. For example, determine how often and for how long the system has been down over the last year and what the business impact was on customers. Use the results of this analysis to drive the HA decision, whether it be a simple, passive-active two machine cluster or a more complex load balancing scenario. On the technical side, NT HA solutions might be appropriate in all-NT shops. At a higher cost, Unix HA solutions have been around longer and provide more choices and tools ranging from simple two-machine clusters to hundred-node clusters.
Andy Gup is software product manager for ADIC (Redmond, WA 425-881-8004 www.adic.com), a manufacturer of tape libraries and storage management software.
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