Perspectives on Cloud Computing

Cloud means many things to many people. Some think cloud computing was invented when HotMail was released in 1996. Is HotMail or any online email system a cloud? If you use Gmail for your email, does that mean you are in the cloud? Maybe.

Defining the Cloud

People who implement clouds define the cloud as a pool of resources available on demand that run in an infrastructure environment. These can be broken down into three layers. Consider these layers of the cloud:

Software as Service

The highest level of applications in the cloud is Software as a Service (SAAS). Gmail, Salesforce.com, Google Apps are all examples of SAAS applications. If your business runs on these applications, you are in the cloud. Advantages of running your applications in the cloud are aplenty: first, your end users will have access to their data and applications from anywhere. No more worrying about VPNs and in most cases (as in Google Apps), no more worry about the platforms your end-users are using. Second, assuming you choose the right service, your data is robust, reliable, and secure.

Platform as a Service

The next level down is Platform as a Service (PAAS). PAAS is a full development stack, running as a service, in the cloud. Examples of PAAS are EngineYard or Heroku for Ruby on Rails development. Services are acquired on demand, resources are metered and billed by usage, and an entire Ruby on Rails stack is available through the service.

Advantages of using PAAS are:
• Pay per use:
• Quick, easy provisioning of resources
• Standardization: all development is done on standard platforms
• Agility: New projects are easy to start; run, expand, and tear down
• Scale up and Scale down: easy to scale up applications as they grow; easy to de-provision applications as they need to be replaced.

Infrastructure as a Service

The lowest level of the cloud is Infrastructure as a Service (IAAS). Infrastructure can be defined as an OS with resources, including compute, memory, storage, and networking. Amazing’s EC2 is an example of a Public Cloud IAAS. Customers can provision, for example, a High CPU Medium Instance. It’s easy to bring up additional instances and add them to the same system. Or de-provision these instances when they are no longer needed. Advantages to an IAAS are the same as PAAS minus the standardization of development platforms.

Public Private Hybrid – What’s this?

Many small to medium size businesses start their operations in a public cloud, such as Amazon EC2. At some point, however, running an entire operation in a public cloud might become cost prohibitive. Or, some companies simply won’t run their operations in a public cloud due to security reasons. It is still possible, however, to leverage the benefits of PAAS and IAAS described above; this is simply implemented as a Private Cloud that runs in a company’s data center (or co-location facility). The Hybrid Cloud is useful when a company wants to leverage multiple resource pools, such as the internal/Private Cloud and possibly a Public Cloud (e.g Amazon). Reasons for doing this are to handle peak demands or for failover / redundancy.