CompTIA® A+ Practical Certification Exam Cram Notes

2. Other Operating Systems & Technologies

2.3 Basic Cloud Concepts

Different cloud models are explained below:

Private cloud: The cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on premise or off premise.

Community cloud: The cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g. mission, security requirements, policy, and compliance considerations). It may be managed by the organizations or a third party and may exist on premise or off premise.

Public cloud: The cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services.

Hybrid cloud: A hybrid cloud includes both the public and private options with one or more providers. By spreading things out over a hybrid cloud, you can keep good control of security and optimize costs. The downside is that you have to keep track of multiple security platforms and ensure that all aspects of your business can communicate with each other.

The primary benefits of the public cloud are:

1. Easy scalability: One of the main benefits that comes with using public cloud services is near unlimited scalability. The resources are usually offered 'on demand' so any changes in activity level can be handled easily. This in turn brings with it cost effectiveness.

2. Cost effectiveness: Since a data center houses hundreds of customer businesses, the hardware and software works out cheaper.

3. Increased reliability: The vast network of servers and the wide bandwidths with which they are inter-linked in public cloud services offers better reliability when compared with private cloud. Even if one data center was to fail entirely, the network simply redistributes the load among the remaining centers making it highly unlikely that the public cloud would ever fail. Also, data centers put lot of resources such as power backups, and backup servers available all the time to cater to any unforeseen events.

The main disadvantage of public cloud over private cloud is with respect to security. Since the public cloud is available on public Internet, it is possible that hackers may attempt to break the services. However, data center companies put several layers of security in a professionally managed data center to make it practically very difficult to bring down a service or application.

The main advantage of private cloud over public cloud is with respect to security. Since the public cloud is available on public Internet, it is possible that hackers may attempt to break the services. A private cloud uses its own server farm, and connected to others resources using private lines, such as a leased line or a VPN.

IAAS (Infrastructure as a Service) : A business may not want to invest into datacenters, servers, networking equipment and the manpower required to maintain all these resources. They may wish to utilize more computer resources as they grow. This is where the Infrastructure as a Service (IAAS) comes in.

The vendors who provide the IAAS maintain all the hardware required so the businesses utilizing their services do not have to worry about it.

IAAS allows organizations to have an unlimited storage potential of the cloud. This allows them to grow and shrink their storage as the requirements demand. The IAAS is used by companies offering disaster recovery services.

SAAS(Software as a Service): also referred to as software on demand, can be used by many people for a variety of functions. It allows users to benefit from the functionality of particular software without having to worry about storage or other issues. The software can easily be accessed by multiple users using just a web browser. Google Docs is a great example of SAAS.

The software is hosted on the cloud servers and requires no installation on client computers in most cases.

PAAS (Platform as a Service): is a variant of SAAS. A client runs their own copies of the Operating System, using the cloud provider's infrastructure. Clients don't have to worry about storage spaces and maintaining servers or hard disks.

NAAS(Network as a Service): Network as a Service (NaaS) is a business model that aims at providing network services over the internet. From a client's point of view, they only require a computer that is connected to the internet - along with the access to NAAS provider's portal.

This is a very cost-effective service that allows new businesses to reduce costs on their network hardware and the required personnel to maintain this hardware. The network just functions on the pay-as-you-go basis, just like water and electricity services.

A few concerns on Cloud technology:

Cloud computing systems are networked systems situated far from subscriber's premises, and are affected by traditional computer and network security issues, such as the need to provide data confidentiality, data integrity, and system availability. Since sensitive customer data resides on the cloud, and usually customers access the cloud using a browser, any browser and communication channel security breaches may directly impact the security of the cloud-based service

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