An Overview of Redundancy
Redundancy is the ability of a system to distribute the load from a failed system across the remaining pieces of equipment without any performance issues or overload. One major issue with colocation facilities is there is no industry standard, regulations or rankings. As a result, it is often difficult to detect the quality of the redundancy systems.
Redundancy Calculation
Redundancy can be calculated with the formula n+1 which indicates that a system is meeting its optimal capacity plus one unit. For instance, if two UPSs are in the overall power system, each should be running at 50 percent to balance the load. If one fails, the other system can maintain the load. If there are three UPSs then each manages 33 percent of the load and if one fails, they each handle half of the third.
In an ideal situation at a colocation facility, systems will be paralyzing redundant with many units running at the n+1 setting with each unit being able to manage the remaining load if all other systems fail.
Powering Redundant Servers
The most important aspect of redundant servers is power. Without it, the equipment will not work thus creating downtime. Power outages can stop the cooling systems (potentially resulting in equipment damage), fire suppressant systems and Internet connections which can be disastrous for the customer.
How to Maintain Redundancy
To maintain redundancy at the server level it is important to keep the colocation facility powered with generators in case of an outage, ensure the generators can handle a large power load and inspect circuit breakers and switches regularly. Switches tend to be the most common point of failure.
The basic premise is that colocation facilities should have backups of everything; backup and redundant servers, backup generators, backup of the backup generators, backup cooling and backup Internet connections. Although it may seem excessive, the clients that rely on these facilities to operate their business expect the best and close to 100 percent uptime. Maintain redundancy at a colocation facility takes a great deal of work to be secure.
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