Certopolis

CompTIA A+ Core 1

IaaS, PaaS, SaaS and public, private, hybrid cloud for A+

The service model says what the customer controls: operating systems and up in IaaS, only its own applications in PaaS, and nothing but user settings in SaaS. The deployment model says who the cloud is for: one organization (private), a group of organizations with shared concerns (community), the general public (public), or two or more of these bound together (hybrid).

Service models: who controls what

IaaS: the customer provisions processing, storage and networks, and controls the operating systems, storage and deployed applications. The provider runs the underlying infrastructure.

PaaS: the customer deploys its own applications built with languages and tools the provider supports. It controls those applications and possibly the hosting environment's settings, but not the network, servers, operating systems or storage.

SaaS: the customer uses the provider's application, for example web-based email in a browser. It controls at most some user-specific settings.

Deployment models: who it is for

Private: for exclusive use by a single organization, which may include several consumers such as business units. It may be run by a third party and may sit off premises. A provider-hosted cloud used only by one hospital group's hospitals is still private.

Community: for exclusive use by a community of consumers from different organizations with shared concerns, such as compliance requirements.

Public: open to the general public, on the provider's premises.

Hybrid: two or more distinct clouds that remain separate but are bound together so data and applications can move between them, for example cloud bursting to handle load.

Elasticity and capacity

NIST lists rapid elasticity among the five essential characteristics of cloud computing, with on-demand self-service, broad network access, resource pooling and measured service.

NIST SP 800-146 says smaller on-site private clouds have capacity limits like traditional data centers. Public clouds have unique advantages in elasticity, the appearance of unlimited resources to consumers. A business with sudden spikes that must pick one model should choose public.

Where the exam catches people

  • Believing a third-party-hosted, off-site cloud cannot be private: NIST says a private cloud may be run by a third party and exist off premises.
  • Believing several hospitals in one group form a community cloud: community means separate organizations; consumers inside one organization make it private.
  • Believing PaaS gives you the operating system: in PaaS you control the deployed applications, not the servers or operating systems.
  • Believing a small on-site private cloud scales like public cloud: its capacity is fixed, like a traditional data center.

Written from CompTIA's documentation

Try 3 questions on this

Pick an answer to see why each option is right or wrong.

  1. A healthcare group owns several hospitals that share the same data-protection compliance requirements. A third-party provider hosts a cloud in its own data center that only the group's hospitals can use. Which of the following cloud models is this?

    Right. In the game that’s Renown for your Virtualization and Cloud Computing building.

    Not that one: B is right. In the game your Virtualization and Cloud Computing building would lose a little Renown, and this question would come back later.

    Show the full explanation and doc quotes

    The hospitals are consumers inside one healthcare group, so the provider-hosted cloud is still private.

    Written from nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-145.pdf

  2. A small development team writes a web application in a language its cloud provider supports. The team uploads only its code and adjusts the hosting settings, while the provider maintains the servers, operating systems and storage. Which of the following cloud models is the team using?

    Right. In the game that’s Renown for your Virtualization and Cloud Computing building.

    Not that one: A is right. In the game your Virtualization and Cloud Computing building would lose a little Renown, and this question would come back later.

    Written from nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-145.pdf

  3. A small retailer runs its online store on servers in its own building. Promotions make traffic jump several-fold without warning, and the retailer wants capacity that grows and shrinks with demand. It will move every system to a single cloud model. Which of the following cloud models should it choose?

    Right. In the game that’s Renown for your Virtualization and Cloud Computing building.

    Not that one: C is right. In the game your Virtualization and Cloud Computing building would lose a little Renown, and this question would come back later.

    Show the full explanation and doc quotes

    Public clouds have unique advantages in achieving elasticity, the appearance to consumers of unlimited resources, so the public cloud is the model whose capacity follows sudden demand.

    Written from nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-146.pdf