> For the complete documentation index, see [llms.txt](https://gyansetu-aws.gitbook.io/aws-cloud/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gyansetu-aws.gitbook.io/aws-cloud/master.md).

# Cloud Computing

**What is Cloud Computing?**

* Cloud computing, often referred to as simply the cloud, is on-demand delivery of IT resources and applications via the Internet with pay-as-you-go pricing.
* With cloud computing, we don’t need to make large up-front investments in hardware and spend a lot of time managing that hardware. Instead, we can provision exactly the right type and size of computing resources we need.
* With cloud computing, we can access as many resources as we need, almost instantly, and only pay for what we use.
* Cloud computing provides  an  easy  way  to access servers,  storage, databases, and a broad set of application services over the Internet.
* Cloud computing providers such as AWS own and maintain the network- connected hardware required for these application services,  while we provision and use what we need for our workloads.

**Advantages of Cloud Computing**

* Low cost
* Usability
* Bandwidth
* Accessibility
* Disaster Recovery
* Secure

**3 ways of cloud compute**

3 building block of cloud computing are

   Saas

   Paas

   Iaas

**Saas (Software as a service)**

Software as a service is the easiest way to cloud compute. The software’s are accessed  over the internet.

Eg. Google doc, spreadsheet etc. Advantage of saas is

* all application is free and paid via subscription.
* Accessible from any computer.

**Paas (Platform as a service)**

Provides   environment  and   tool  for   creating   new   online applications

Eg. Google app engine, salesforce (force.com)

**Advantages**

   Facilitation of hosting capabilities.

   Designing and developing the application.

   Private or public deployment.

**Disadvantage**

   Application build on one vendor cannot be moved to another.

**Iaas (Infrastructure as a Service)**

Allow existing application to run on a cloud supplier’s hardware. Iaas comes in 4 categories

1\.  Private cloud

2\. Dedicated host

3\. Hybrid hosting

4\. Cloud hosting

Aws works on iaas.

**Advantages**

   The application is hosted centrally

   Software testing takes place at a faster rate

   Reduction in IT operational cost.

**Cloud types**

* Public cloud
* Private cloud
* Hybrid cloud
* Community cloud

**Public Cloud**

* Service  providers  use  the  internet  to  make  resources,   such  as applications, storage
* Examples  of public clouds include Amazon web service, IBM’s  Blue Cloud, Sun Cloud, Google compute engine and Windows Azure Services Platform.
* For users, these types of clouds will provide the best economies of scale,  are inexpensive to set-up because  hardware, application and bandwidth costs  are covered by the provider.  It’s a pay-per-usage model and the only costs  incurred are based on the capacity that is used.

**Disadvantages**

* the public cloud may not be the right fit for every organization. The model can limit configuration, security, and SLA specificity, making it less-than-ideal for services  using sensitive  data that is  subject  to compliancy regulations

**Private cloud**

* Private  clouds are  data  center  architectures   owned  by  a  single company that provides flexibility, scalability, provisioning, automation and monitoring.
* The  goal of a private cloud is  not sell  “as-a-service”  offerings  to external customers but instead to gain the benefits of cloud architecture without giving up the control of maintaining your own data center.
* Private  clouds  can  be expensive,  so  most  typically  use  by large enterprises.  Private clouds are driven by concerns  around security and compliance, and keeping assets  within the firewall.

**Hybrid Cloud**

* By using a Hybrid approach, companies  can maintain control of an internally managed private cloud while relying on the public cloud as needed.  For instance, during peak periods individual applications, or portions of applications can be migrated to the Public Cloud.
* This  will  also  be beneficial  during predictable outages:  hurricane warnings, scheduled maintenance windows, rolling brown/blackouts.

**Community Cloud**

* A community  cloud is  a  multi-tenant  infrastructure  that  is  shared among several  organizations  from a specific  group with common computing concerns.