CloudDB AutoAdmin - Large Scale and Big Data: Processing and Management - page 360

particular, there are three typical parties in the cloud. To keep a consistent terminol-
ogy throughout the rest of the chapter, these parties are defined as follows:

• Cloud Service Providers (CSP) : They offer client-provisioned and metered

computing resources (e.g., CPU, storage, memory, network) that can be
rented for flexible time durations. In particular, they include Infrastructure-
as-a-Service providers (IaaS), Platform-as-a-Service providers (PaaS), and
Database-as-a-Service (DaaS). Examples include Amazon, Microsoft, and
Google.

• Cloud Consumers : They represent the cloud-hosted software applications

that utilize the services of CSP and are financially responsible for their
resource consumptions.

• End Users : They represent the legitimate users for the services (applica-

tions) that are offered by cloud consumers.

While cloud service providers charge cloud consumers for renting computing
resources to deploy their applications, cloud consumers may charge their end users
for processing their workloads (e.g., SaaS) or may process the user requests for free
(cloud-hosted business application). In both cases, the cloud consumers need to guar-
antee their users' SLA. Penalties are applied in the case of SaaS and reputation loss
is incurred in the case of cloud-hosted business applications. For example, Amazon
found that every 100 ms of latency costs them 1% in sales and Google found that an
extra 500 ms in search page generation time dropped traffic by 20%.* In addition,
large enterprise web applications (e.g., eBay, Facebook) need to provide high assur-
ances in terms of SLA metrics such as response times and service availability to
their users. Without such assurances, service providers of these applications stand to
lose their user base, and hence their revenues.
In practice, resource management and SLA guarantee falls into two layers: the
cloud service providers and the cloud consumers. In particular, the cloud service
provider is responsible for the efficient utilization of the physical resources and guar-
antee their availability for their customers (cloud consumers). The cloud consumers
are responsible for the efficient utilization of their allocated resources to satisfy the
SLA of their customers (end users) and achieve their business goals. Therefore, we
distinguish between two types of service level agreements (SLAs):

1. Cloud Infrastructure SLA (I-SLA) : These SLAs are offered by cloud provid-
ers to cloud consumers to assure the quality levels of their cloud computing
resources (e.g., server performance, network speed, resources availability,
storage capacity).

2. Cloud-hosted Application SLA (A-SLA) : These guarantees relate to the lev-
els of quality for the software applications, which are deployed on a cloud
infrastructure. In particular, cloud consumers often offer such guarantees to
their application's end users to assure the quality of services that are offered
such as the application's response time and data freshness.

* http://glinden.blogspot.com/2006/11/marissa-mayer-at-web-20.html.