Information Technology Reference
In-Depth Information
3 Deployment and Execution Using the IAAS Cloud
As shown in Figure 1 the life cycle of a Cloud application that is running by
using a Cloud infrastructure is divided into three phases:
1.
Cloud Provisioning
. The user hasto choosethe best Cloud resourcesforhis/her
application (e.g. VMs, storages, etc.). After that he/she has to select the best
IaaS provider basing his/her thinking on a lot of parameters (cost per use,
amount of VM memory, storage's size, bandwidth, etc.). Many times this rea-
soning is too dicult because each provider offers its resources highlighting
different characteristicsand parameters. This happens because the Cloud ven-
dors haven not a common and standardized interface to describe the resource
parameters, making the comparison among same resources an hard job.
2.
Cloud Configuration
. After selecting the best resources for his/her applica-
tion, the Cloud customer needs to sign an SLA with a Cloud vendor. Once
this has been done some management activities are carried before deploying
applications. For instance OS images have to be attached and the purchased
VMs have to be started. For this reason, the cloud user/developer has to
know the allowed actions for that resource and the service interface for that
Cloud provider. In fact the same resource purchased from a different provider
have different interface and different supported functionalities. At this point
the Cloud application can be deployed and executed.
3.
Cloud Monitoring
. Here Cloud users configure a network of probes that col-
lects measures about the performance parameters of the Cloud resources.
To get an up to date knowledge of Cloud performance and an history of
the Cloud behavior it needs to periodically compute a set of performance
indexes and to set up some triggers which notify critical conditions. In fact it
would be useful to know if the workload of the infrastructure is different from
the one foreseen, in order to avoid saturation or under-utilization of Cloud
resources. This information is necessary to design effective reconfigurations
of the infrastructure, in order to better adapt it to the current application
requirements and to optimize performances and costs.
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Fig. 1.
Deployment and execution workflow by using IAAS Cloud
