Warranty and support
Servers are designed to be more reliable. And it is possible to purchase and configure a server installation that will guarantee just about 100 percent availability. This can be achieved by building in complete system redundancy - the server will continue to operate despite the failure of one or more parts.
However, this type of configuration has two drawbacks - cost and complexity. Often the cost for permanent uptime is far beyond the losses that would be incurred should the server fail.
The reliability of a server installation is a trade-off between the amount spent on building in redundancy versus the losses incurred financially and to reputation in the event of server 'downtime'.
Server vendors know this. Consequently they provide not only a range of hardware with varying levels of reliability, but also support services of varying responsiveness.
Most servers come with three years parts and labour warranty. Generally, this is a Monday to Friday, business hours, on-site warranty. In other words, they will come to your site to fix the problem by the end of the next business day.
Of course, this means that should your server fail at 9am on a Friday, the vendor is obliged to fix it by the end of business the following Monday. While most vendors will endeavour to do better, your server could be out of operation for 80 hours over the weekend.
Consequently server vendors will sell you guaranteed response times, generally four-hour or two-hour. These can also be purchased for business hours Monday to Friday or 24 hours a day, 7 days a week.
The support option you choose will be dictated by the redundancy level of the server(s) you have purchased, the cost of the support options, and the losses that may be incurred from downtime.
It is also possible to purchase warranty extensions for new hardware to extend the warranty beyond three years. Most vendors will sell you these warranty extensions both at the time of server purchase or prior to the three-year warranty expiring.