Cloud computing is a model for enabling ubiquitous, convenient, and on-demand network access to a shared pool of resources. These computing resources can be rapidly provisioned and released with minimal effort. The Cloud model is composed of three service models, seen below:
Software as a Service (SaaS)
- SaaS is the most familiar form of cloud service for consumers.
- SaaS redistributes the task of managing software and its deployment to third-party services.
- Among the most familiar SaaS applications for business are customer relationship management applications like Salesforce, productivity software suites like Google Apps, and storage solutions brothers like Box and Dropbox.
- Use of SaaS applications tends to reduce the cost of software ownership by removing the need for technical staff to manage install, and upgrade software.
- SaaS applications are usually provided on a subscription model.
Adobe Connect, ServiceNow, Google, Salesforce, Microsoft O365, MaaS360
Common SaaS Use-Case:
Replaces traditional on-device software. There are a wide variety of cases including Customer Relationship Management, Video Conferencing, Email, Collaboration, and more. SaaS services allow direct delivery of application level capabilities to the end user with very little requirement for IT support resources primarily focused on compliance management at the application layer.
SaaS Model Customer Responsibilities include:
- See also “Shared Responsibility Model” below.
Platform as a Service (PaaS)
- PaaS functions at a lower level than SaaS, typically providing a platform on which software can be developed and deployed.
- As with most cloud services, PaaS is built on top of virtualization technology. Businesses can requisition resources as they need them, scaling as demand grows, rather than investing in hardware with redundant resources.
- The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, and deployed applications; and possibly limited control of select networking components (e.g. host firewalls).
ESRI Managed Services Cloud, MicroPact, Oracle Federal Cloud, Cloud.gov
Common PaaS Use-Case:
Increases developer productivity and utilization rates while also decreasing an application’s time-to-market. Consumers of PaaS services will need minimum IT services administration staff since management of the Operating Systems, Middleware, Databases are covered by the vendor.
PaaS Model Customer Responsibilities include:
- See also the “Shared Responsibility Model” below.
Infrastructure as a Service (IaaS)
- IaaS providers offer these cloud servers and their associated resources via dashboard.
- IaaS clients have direct access to their servers and storage, just as they would with traditional servers but gain access to a much higher order of scalability.
- Users of IaaS can outsource and build a “virtual data center” in the cloud and have access to many of the same technologies and resource capabilities of a traditional data center without having to invest in capacity planning or the physical maintenance and management of it.
- IaaS is the most flexible cloud computing model and allows for automated deployment of servers, processing power, storage, and networking.
- IaaS clients have true control over their infrastructure than users of PaaS or SaaS services.
Amazon Web Services, Microsoft, Azure, IBM SoftLayer, Virtustream, Akamai
Common IaaS Use-Case:
Extends current data center infrastructure for temporary workloads (e.g. increased Christmas holiday site traffic). Consumers of IaaS services will be required to have skilled IT professionals on staff or available via contract to manage and maintain Operating Systems, Middleware, Databases, Operations and Compliance Management.
IaaS Model Customer Responsibilities include:
- Operating System
- Virtual Network
- See also the “Shared Responsibility Model" below.
Shared Responsibility Model:
- Customer's responsibility: People, Data
- CSP responsibility: Applications, Runtime, Middleware, Operating System, Virtual Network, Hypervisor, Servers, Storage, Physical Network
- Customer's responsibility: People, Data, Applications
- CSP responsibility: Runtime, Middleware, Operating System, Virtual Network, Hypervisor, Servers, Storage, Physical Network
- Customer's responsibility: People, Data, Applications, Runtime, Middleware, Operating System, Virtual Network
- CSP responsibility: Hypervisor, Servers, Storage, Physical Network