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Two Nines

The Computer Corner

By Charles Miller

Sometimes people who live in San Miguel de Allende fail to appreciate how lucky they are to live in a community where they can have access to so much reliable and affordable modern technology. On those occasions when Internet connectivity is interrupted for a few minutes or hours, people are quick to forget that two decades ago in San Miguel two of the most commonly asked questions were “Could you get a dial tone yesterday?” or “How many hours was your electricity off?” Today, the electric and communications services in San Miguel have been modernized and are far better than 99 percent reliable. This is what we in IT call “two nines.”

Three nines (99.9 percent) is better than two but more expensive, and four nines even better. Among computer techs the holy grail of reliability is called “five nines” or 99.999 percent uptime.

In order to achieve 99.999 percent reliability a system cannot not have more than five minutes and 35 seconds of downtime in a calendar year; that is less than one second per day. As a practical matter, achieving this would require that there be a redundant system in place and that any and all connectivity problems would automatically switch your Internet connection to a backup system in a split second. That is the kind of redundancy large online vendors such as use because they cannot afford to be offline for one second. To serve the home market, Internet providers have to deal with the fact that trees fall down across overhead lines, squirrels chew through wires, or when it rains, water can get into lines. These outages simply cannot be rectified in a matter of seconds, and so a realistic and achievable goal for most infrastructure systems is two nines.

Corporate bean counters can verify there is an unscientific, albeit fairly accurate, collation between cost and reliability: Every extra decimal of increased reliability equates more or less to an extra decimal of cost. As applied to the individual Internet user, what this means is that in your home if you are using a low-cost Internet service that is 99 percent reliable and paying 300 pesos a month for it, taking all the steps necessary to improve the reliability of your Internet service to three nines or 99.9 percent could cost you 3,000 pesos or more per month.

The fact is, the Internet connectivity and the electric utility in San Miguel are very reliable. I once measured my Internet uptime as 99.6 percent over one year, and judging by the number of times my digital clock says 12:00, 12:00, 12:00, I would estimate that CFE is achieving better than four nines or 99.99+ percent reliability.

Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981 and now practically a full-time resident. He may be contacted at 044-415-101-8528 or email FAQ8 (at)


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