Public

Public is the typical IaaS-compute deployment model most people think of when referring to the cloud. A public cloud service provider offers IT resources as-a-service and, as part of the service, is responsible for building, monitoring, and maintaining physical data centers and IT resources that are for dynamic public consumption. This IT service environment is shared among many customers which normally reduces costs for each customer. By leveraging economies of scale, the CSP enables higher average utilization of resources through the extensive use of virtualization, workload binding, offsetting clients workload patterns, and performance tiers.

The general public uses a public cloud infrastructure. The infrastructure may be owned, managed, and operated by a business, academic, or government organization, or some combination. The infrastructure is always on service provider premises as they have taken ownership of operations and maintenance. Amazon is a good example. The business started off by selling books. It then started to sell excess server and storage capacity to the general public. The infrastructure remained on-premise at Amazon locations.

A public cloud can fall into two sub-types within IaaS, self managed or fully managed. Both of these sub-types are discussed in greater detail later in this chapter. A public cloud is highly scalable, immediately deployed, portal driven, and can be parked or turned off when not in use.

Public cloud benefits include:

• Ease of use and inexpensive setup, low cost of entry to the cloud
• Streamlined and easy-to-provision resources via a self-serve portal
• Scaled to meet customer needs 
• No wasted resources because customers pay only for what they consume
• Basic security services included

Public cloud considerations are:

• How are noisy neighbors handled?
• Does security line up with my requirements?
• Is there any network access or storage limitations?
• Cost of access or data transfer in/out?
• Portability? Grow into other instance types and service types?
• What other services connect to it?
• What is the price/performance metric?

Providers often mentioned in this space include Amazon, Microsoft, and Google, among others.