CloudDB AutoAdmin - Large Scale and Big Data: Processing and Management - page 359

provisioning the database tier based on the consumer-centric SLA metric of data
freshness is presented in Section 11.6 and for the SLA metric of the response times
of application transactions is presented in Section 11.7. Section 11.8 summarizes the
related work before we conclude the chapter in Section 11.9.
11.2 VIRTUALIZED DATABASE SERVER
Virtualization is a key technology of the cloud computing paradigm. Virtual machine
technologies are increasingly being used to improve the manageability of software
systems and lower their total cost of ownership. They allow resources to be allocated
to different applications on demand and hide the complexity of resource sharing from
cloud users by providing a powerful abstraction for application and resource provision-
ing. In particular, resource virtualization technologies add a flexible and programmable
layer of software between applications and the resources used by these applications.
The virtualized database server approach takes an existing application that has been
designed to be used in a conventional data center, and then port it to virtual machines
in the public cloud. Such migration process usually requires minimal changes in the
architecture or the code of the deployed application. In this approach, database serv-
ers, like any other software components, are migrated to run in virtual machines. Our
framework presented in this chapter belongs to this approach .
In principle, one of the major advantages of the virtualized database server
approach is that the application can have full control in dynamically allocating and
configuring the physical resources of the database tier (database servers) as needed
[5,17,20]. Hence, software applications can fully utilize the elasticity feature of the
cloud environment to achieve their defined and customized scalability or cost reduc-
tion goals. However, achieving these goals requires the existence of an admission
control component, which is responsible for monitoring the system state and taking
the corresponding actions (e.g., allocating more/less computing resources) according
to the defined application requirements and strategies. Several approaches have been
proposed for building admission control components that are based on the efficiency
of utilization of the allocated resources [5,20]. In our approach, we focus on build-
ing an SLA-based admission control component as a more practical and consumer-
centric view for achieving the requirements of their applications.
11.3 CHALLENGES OF SLA MANAGEMENT FOR
VIRTUALIZED DATABASE SERVERS
An SLA is a contract between a service provider and its customers. Service level
agreements (SLAs) capture the agreed upon guarantees between a service provider
and its customer. They define the characteristics of the provided service including
service level objectives (SLOs) (e.g., maximum response times, minimum through-
put rates, data freshness) and define penalties if these objectives are not met by the
service provider. In general, SLA management is a common general problem for
the different types of software systems, which are hosted in cloud environments
for different reasons such as the unpredictable and bursty workloads from various
users in addition to the performance variability in the underlying cloud resources. In