Most cloud computing infrastructures consist of services delivered through common centers and built on servers. Clouds often appear as single points of access for consumers’ computing needs. Commercial offerings are generally expected to meet quality of service (QoS) requirements of customers, and typically include service level agreements (SLAs).[9] The major cloud service providers include Amazon, Salesforce, Microsoft and Google.[10][11] Some of the larger IT firms that are actively involved in cloud computing are Fujitsu, Dell, [12] Red Hat, [13] Hewlett Packard,[14] IBM,[15] VMware and NetApp.
