Reliability is something which is very risky and dangerous too. Because the person on whom you are relying will make you fall is completely unknown to you. Similarly, due to increasing competition pressure, a hosting provider can make unrealistic promises or benefits such as 100% uptime.
Any web hosting which flaunts a rate of 99.99 percent uptime, it suggests that they are given the protection of about 53 minutes facing the yearly outrage time. This outage time includes server downtime, regular routine maintenance or unprecedented failures. Like, service actors denial for highly congested sites that in turn makes the server overpopulated. If you see a higher uptime advertisement, the shorter the margin of error and disaster a web host has permitted to themselves.
At times, internet connectivity loses and websites become unavailable for several unexpected reasons.
In that case, any hosting advertisers of having a 100% uptime, people have the curiosity to ask them about the measures they have taken to prevent outage time. Their answer to this must include the following terminologies: full redundancy, mirroring, disk arrays, air-conditioner, system administrators and an uninterrupted power supply. But be aware of the fact that there is nothing called 100% uptime in reality.