Information Technology Reference
In-Depth Information
the provider also rents standard software such as databases and rudimentary
database management services as part of their service offering.
Similar to the colocation scenario, contracting with a managed-service
provider typically involves at minimum an annual commit, with an initial
setup fee followed by a recurring monthly charge based on the configura-
tion of hardware and software being rented. In this model, bandwidth is not
typically charged for separately; instead, you get a standard allotment based
on the number of servers for which you contracted. You can also contract
for ancillary services, such as backups. Typically, the charge is based on the
amount of storage required on a monthly basis (Tables 14.2 through 14.4).
14.3.4 IaaS Cloud Model
Finally, we get to the cloud model. In this model, as in the managed-service
model, the company outsources the infrastructure and hardware, but in an
entirely different way. Instead of dedicated hardware resources, the company
utilizes virtualized resources that are dynamically allocated only at the time of need.
We can think of this as the analog of just-in-time manufacturing, which
brought tremendous efficiencies to the production of goods. Instead of stock-
piling large inventories, manufacturers can reduce their carrying costs by
having inventory delivered just as it is needed in manufacturing. Similarly,
the dynamic allocation of resources in a cloud service allows a customer to
use computing resources only when necessary. Servers do not have to sit idle
during slack periods.
The billing model for cloud services is aligned with this sort of usage pro-
file, with service provisioning often requiring no up-front cost and monthly
billing based on the actual amount of resources consumed that month. This
may translate into significant cost advantages over traditional deployment
models.
14.4 Quality of Service (QoS)
QoS refers to the ability of the cloud service to respond to expected invo-
cations and to perform them at the level commensurate with the mutual
expectations of both its provider and its customers. Several quality factors
that reflect customer expectations, such as constant service availability, con-
nectivity, and high responsiveness, become key to keeping a business com-
petitive and viable as they can have a serious impact upon service provision.
QoS thus becomes an important criterion that determines the service usabil-
ity and utility, both of which influence the popularity of a particular cloud
service, and an important selling and differentiating point between cloud
services providers.
Search WWH ::




Custom Search