Uptime is probably the most important single metric you can use to measure the performance of your web host. It shows the time or percentage the service is up and operational. The counterpart of that is downtime. It shows the time or percentage the service was unavailable.
Availability is the same as uptime. It’s often measured by “Nines.” Let’s see how they translate to downtime for 30 days:
|NINES||DOWNTIME ( for 30 days )|
|99%||Two Nines equals to 7 hours and 12 minutes downtime in 30 days|
|99.9%||Three Nines equals to 43 minutes and 12 seconds downtime|
|99.99%||Four Nines equals to 4 minutes 19 seconds downtime|
|99.999%||Five Nines equals to 26 seconds downtime|
|99.9999%||Six Nines equals to 3 seconds downtime|
Some of the web hosting companies offer a Service Level Agreement. It states the guaranteed level of availability. If the web host doesn’t deliver that uptime level, you will be entitled to refunds or hosting credits. Use our uptime calculator to quickly see if your provider delivered.
Some web hosts offer real uptime guarantees. Others just say they have a 99.9% uptime guarantee but if you take a look at the terms of service they make you agree with, most of the times you will notice that they do not guarantee it for real. If they don’t deliver the uptime they promised, nothing happens.