38 IBM System Storage Solutions for Smarter Systems
3.1 Cloud computing models
While cloud computing is still a relatively new technology, there are generally three cloud
service models, each with a unique focus. The American National Institute of Standards and
Technology (NIST) has defined the following cloud service models:
Software-as-a-Service (SaaS): “The capability provided to the consumer is to use the
provider's applications running on a cloud infrastructure. The applications are accessible
from various client devices through a thin client interface, such as a web browser (for
example, web-based email). The consumer does not manage or control the underlying
cloud infrastructure including network, servers, operating systems, storage, or even
individual application capabilities, with the possible exception of limited user-specific
application configuration settings.
Platform-as-a-Service (PaaS): “The capability provided to the consumer is to deploy onto
the cloud infrastructure consumer-created or acquired applications created using
programming languages and tools supported by the provider. The consumer does not
manage or control the underlying cloud infrastructure, including network, servers,
operating systems, or storage, but has control over the deployed applications and possibly
application hosting environment configurations.
Infrastructure-as-a-Service (IaaS): “The capability provided to the consumer is to
provision processing, storage, networks, and other fundamental computing resources
where the consumer is able to deploy and run arbitrary software, which can include
operating systems and applications. The consumer does not manage or control the
underlying cloud infrastructure but has control over operating systems, storage, deployed
applications, and possibly limited control of select networking components (for example,
Figure 3-1 depicts some of the cloud computing solutions that are currently available.
Figure 3-1 Examples of SaaS, PaaS, and IaaS services offered by cloud computing
© 2009 IBM Corporation
Infrastructure-as-a-Service (IaaS)
Platform-as-a-Service (PaaS)
Software-as-a-Service (SaaS)
Servers Networking Storage
Data Center
Shared virtualized, dynamic provisioning
Web 2.0 Application
Chapter 3. Flexible delivery solutions 39
In addition, NIST has also defined the following models for deploying cloud services:
Private cloud: “The cloud infrastructure is owned or leased by a single organization and is
operated solely for that organization.
Community cloud: “The cloud infrastructure is shared by several organizations and supports
a specific community that has shared concerns (for example, mission, security requirements,
policy, and compliance considerations).
Public cloud: “The cloud infrastructure is owned by an organization selling cloud services to
the general public or to a large industry group.
Hybrid cloud: “The cloud infrastructure is a composition of two or more clouds (internal,
community, or public) that remain unique entities but are bound together by standardized or
proprietary technology that enables data and application portability (for example, cloud
Figure 3-2 summarizes several deployment models used for cloud services.
Figure 3-2 Cloud computing deployment models
From a storage perspective, IBM clients, based on their business requirements, can choose
to adopt either a pubic or private storage cloud. These storage clouds are defined as follows:
Public storage cloud: This is designed for clients who do not want to own, manage, or
maintain the storage environment, thus reducing their capital and operational expenditures
for storage. IBM dictates the choice of technology and cloud location, shared infrastructure
with variable monthly charges, dynamic physical capacity at the customer level, and
security measures to isolate customer data. The public storage cloud allows for variable
billing options and shared tenancy of the storage cloud, giving customers the flexibility to
manage the use and growth of their storage needs. This is the industry standard view of a
storage cloud offering and is comparable to storage cloud offerings by other vendors.

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