More and more companies provide high availability solutions for customers to improve the uptime now.  The customer pay a little bit more and get a more robust and stable solutions. Some company even claim 100% uptime, or 99.9999% uptime ganrantee.  These are very good for those critical business web site, like ecommerce web site.

One thing need to note is that these enhanced solutions are normally focused on the server and database.  Whether your site is accessible or not is not only depending on your server's availability, it is also depending on things like network bandwidth, the customer's Internet connection, etc.

The commonly used terms for the enhanced solutions are "Failover Hosting" and "Grid Hosting".  They can both resolve the situation that when one or more servers are down, other servers can take over the remaining work and finish the process succesfully.

• What is Failover Hosting? 

High-availability clusters (also known as HA Clusters or Failover Clusters) are computer clusters that are implemented primarily for the purpose of providing high availability of services which the cluster provides. They operate by having redundant computers or nodes which are then used to provide service when system components fail. 

Hosting Zoom provides Failover web hosting package and reseller package.

• What is Grid Hosting? 

Grid is a cluster-based, modern hosting service powered by hundreds of servers working in tandem to power your websites.  Grid hosting makes it less likely that a spike in resource needs will take your site offline.

GoDaddy provides grid web hosting packages.