Information Technology Reference
In-Depth Information
used to support operations, including storage,
hardware, servers and networking components. In
that case the provider is the owner of the hardware
equipment and all relevant resources and expenses
related to housing, constant operation and main-
tenance are his own responsibility. The client
typically pays on a per-use basis. Infrastructure
as a Service involves the physical storage space
and processing capabilities that enable the use of
SaaS and PaaS if wanted otherwise these services
are used autonomously by the customer. Virtu-
alization enables IaaS providers to offer almost
unlimited instances of servers to customers and
make cost-effective use of the hosting hardware.
IaaS can be exploited by enterprises that chase
quick time to market. The customer enterprise can
accelerate the development time required to build
new versions of applications or environments
without having to worry about ordering, waiting,
paying and configuring new hardware equipment.
The most popular use of IaaS is website hosting.
Website hosting is a convenient way for enterprises
to shift the relevant IT resources away from an
internal infrastructure whose primary purpose is
to run the business, not the website. In this case
the availability and the monitoring of the website
are in the concerns of the IaaS provider.
IaaS offers relatively simple infrastructure as
it includes basic hardware and operating services.
Customers select software servers with operating
systems that match their needs and then they load
up their own libraries, applications and data and
finally configure them themselves. This process
requires that the in-house personnel possess con-
siderable IT skills. In the case that the customer
enterprise personnel is relatively inexperienced
IaaS may not be enough to cover the needs of
the customer and can be combined with PaaS.
IaaS is then enriched with platform services such
as database management systems, web hosting
server software, batch processing software and
application development environments that are
installed in the relevant infrastructure. PaaS and
IaaS costs in that case are interrelated.
IaaS and PaaS are billed based on the services
delivered to the customer. The billing model is pro-
duced considering the level of usage of hardware,
application, storage and networking components.
Hardware and application components are usually
charged simultaneously. These costs most of the
times are calculated as on-demand instances per
hour. On-Demand instances refer to the number
of servers used. The prices differ according to
the operating systems and middleware applica-
tions loaded to the offered servers. The payment
is then processed based on per use instances that
are indicative of the compute capacity. Additional
metrics that can be used derive from the technical
attributes of the server such as the hard disk size
of the server, the cpu and the memory capacity.
The usage of the servers may also be charged
measured in bandwidth or as a daily percentage
usage, along with additional IP generation. Also
full back ups of cloud servers may be charged
separately. PaaS services that may be included in
the prices involve databases, web servers, applica-
tion development environments and servers and
video encoding and streaming software.
Storage services are billed based on the hard
disk demands, the data transfer and the requests.
Initially the data storage is measured in terabytes
committed in the hard disk. The price depends on
the level of hard disk usage. Data transfer involves
transferring the data into databases. Data transfer
may be charged autonomously, or is included in
data storage fees or may be for free based on the
regions of transfer. Data requests involve opera-
tions such as copy, get, put, list and other requests
regarding the data. Data requests involve inquiries
in the data set.
Networking services involves the possibility
of establishing a virtual private cloud (Amazon,
VPC) that will be the bridge between a company's
existing IT infrastructure and the cloud. A private
cloud enables enterprises to connect their existing
infrastructure to a set of isolated cloud compute
resources via a Virtual Private Network (VPN)
connection, and to extend their existing manage-
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