Reliability is critical. Unfortunately, competitive pressures can drive a hosting provider to
make unrealistic promises, such as 100% uptime.
When a web hosting advertises a 99.99 percent uptime, this gives them a cushion of about 53 minutes of
outage time a year. This includes server down time due to regular scheduled maintenance or unexpected
disasters (such as denial of service attacks, or overly popular websites that overload the server).
The higher the advertised uptime, the narrower the margin for error and disasters a web host has allowed themselves.
We all know that Internet connections do go down, and that websites do become temporarily unavailable for
all sorts of intentional and unpreventable reasons.
If your web host advertises 100% uptime, you may want to ask them about the measures they have take to make sure
a guarantee. Their answer should include the following terms: fully redundancy, mirroring, disk arrays, air conditioner,
system administrators, and uninterruptible power supply. But still, keep in mind that there is no such thing as 100% uptime.