Cloud Computing

Cloud Computing - Public and Private

Cloud computing is a general term for anything that involves delivering hosted services over the Internet. These services are broadly divided into three categories: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). The name cloud computing was inspired by the cloud symbol that's often used to represent the Internet in flowcharts and diagrams.

A cloud service has three distinct characteristics that differentiate it from traditional hosting. It is sold on demand, typically by the minute or the hour; it is elastic -- a user can have as much or as little of a service as they want at any given time; and the service is fully managed by the provider (the consumer needs nothing but a personal computer and Internet access). Significant innovations in virtualization and distributed computing, as well as improved access to high-speed Internet and a weak economy, have accelerated interest in cloud computing.

A cloud can be private or public. A public cloud sells services to anyone on the Internet. (Currently, Amazon Web Services is the largest public cloud provider.) A private cloud is a proprietary network or a data center that supplies hosted services to a limited number of people. When a service provider uses public cloud resources to create their private cloud, the result is called a virtual private cloud. Private or public, the goal of cloud computing is to provide easy, scalable access to computing resources and IT services.
Infrastructure-as-a-Service like Amazon Web Services provides virtual server instanceAPI) to start, stop, access and configure their virtual servers and storage. In the enterprise, cloud computing allows a company to pay for only as much capacity as is needed, and bring more online as soon as required. Because this pay-for-what-you-use model resembles the way electricity, fuel and water are consumed, it's sometimes referred to as utility computing.
Platform-as-a-service in the cloud is defined as a set of software and product development tools hosted on the provider's infrastructure. Developers create applications on the provider's platform over the Internet. PaaS providers may use APIs, website portals or gateway software installed on the customer's computer. Force.com, (an outgrowth of Salesforce.com) and GoogleApps are examples of PaaS. Developers need to know that currently, there are not standards for interoperability or data portability in the cloud. Some providers will not allow software created by their customers to be moved off the provider's platform.
In the software-as-a-service cloud model, the vendor supplies the hardware infrastructure, the software product and interacts with the user through a front-end portal. SaaS is a very broad market. Services can be anything from Web-based email to inventory control and database processing. Because the service provider hosts both the application and the data, the end user is free to use the service from anywhere.

Hybrid Cloud

A hybrid cloud is a composition of at least one private cloud and at least one public cloud. A hybrid cloud is typically offered in one of two ways: a vendor has a private cloud and forms a partnership with a public cloud provider, or a public cloud provider forms a partnership with a vendor that provides private cloud platforms.

 A hybrid cloud is a cloud computing environment in which an organization provides and manages some resources in-house and has others provided externally. For example, an organization might use a public cloud service, such as Amazon Simple Storage Service (Amazon S3) for archived data but continue to maintain in-house storage for operational customer data. Ideally, the hybrid approach allows a business to take advantage of the scalability and cost-effectiveness that a public cloud computing environment offers without exposing mission-critical applications and data to third-party vulnerabilities.  This type of hybrid cloud is also referred to as hybrid IT.

Cloud Backup (online backup)

Cloud backup, also known as online backup, is a strategy for backing up data that involves sending a copy of the data over a proprietary or public network to an off-site server. The server is usually hosted by a third-party service provider, who charges the backup customer a fee based on capacity, bandwidth or number of users. In the enterprise, the off-site server might be proprietary, but the chargeback method would be similar.

Online backup systems are typically built around a client software application that runs on a schedule determined by the level of service the customer has purchased. If the customer has contracted for daily backups, for instance, then the application collects, compresses, encrypts and transfers data to the service provider's servers every 24 hours. To reduce the amount of bandwidth consumed and the time it takes to transfer files, the service provider might only provide incremental backups after the initial full backup.

Third-party cloud backup has gained popularity with small offices and home users because of its convenience. Capital expenditures for additional hardware are not required and backups can be run dark, which means they can be run automatically without manual intervention.

In the enterprise, cloud backup services are primarily being used for archiving non-critical data only. Traditional backup is a better solution for critical data that requires a short recovery time objective (RTO) because there are physical limits for how much data can be moved in a given amount of time over a network. When a large amount of data needs to be recovered, it may need to be shipped on tape or some other portable storage media. (See:AWS import-export)

Russ Fellows, Senior Analyst with the Evaluator Group, has put together the following chart to illustrate when cloud backups should be considered as a viable option.

Backup factor	Cloud storage	Traditional backup
Amount of data	Best when the total amount to protect is less than 100 GB per 1 Mb of network bandwidth. For example, 100 GB can be supported by a 1 Mb WAN connection (such as DSL)	For large amounts of data, or for environments with limited network connectivity, traditional backup techniques are more appropriate.
Rate of change	Best when the rate of change is less than 10% of the total data per month.	For data that changes frequently, traditional backup methods that use local disk and tape, with tape transport off-site are more appropriate