Cloud Hosting: The Truth About Cloud Web Hosting (page 1).
In general, the actual cloud hosting platform serves different hosting services like disk storage, mail, FTP, databases, DNS, statistics, Control Panel, backup, etc. on separate groups of very powerful servers. Each separate service group forms a cluster. All the servers in a cluster are dedicated to serving only the given service and nothing else. They will all work as one server, sharing the service's load in almost equal proportions. If there is a real cloud hosting service, there would be: a disk storage cluster, a mail cluster, an FTP cluster, database clusters (MySQL/PostgreSQL), a DNS cluster, a statistics cluster, a Control Panel cluster, a backup cluster, etc. All these different service clusters will form the so-called cloud hosting platform.