Cloud computing is very attractive to the users:
Economic reasons.
low infrastructure investment.
low cost – customers are only billed for resources used.
Convenience and performance.
application developers enjoy the advantages of a just-in-time
infrastructure; they are free to design an application without being
concerned with the system where the application will run.
the execution time of compute-intensive and data-intensive applications
can, potentially, be reduced through parallelization.  If an application can
partition the workload in
n
segments and spawn
n
instances of itself, then
the execution time could be reduced by a factor close to
n
.
✒ Cloud computing is also beneficial for the providers of computing cycles -
it typically leads to a higher level of resource utilization.

SLA – a negotiated contract between the customer and CSP; can be
legally binding or informal. Objectives:
• Identify and define the customer’s needs and constraints
including the level of resources, security, timing, and QoS.
• Provide a framework for understanding; a critical aspect of
this framework is a clear definition of classes of service and
the costs.
• Simplify complex issues;  clarify the boundaries between the
responsibilities of clients and CSP in case of failures.
• Reduce areas of conflict.
• Encourage dialog in the event of disputes.
• Eliminate unrealistic expectations.
• Specifies the services that the customer receives, rather than how
the cloud service provider delivers the services.

Windows Azure
- an operating system; has 3
components:
• Compute – provides a computation environment.
• Storage – for scalable storage.
• Fabric Controller – deploys, manages, and monitors
applications.
•SQL Azure
- a cloud-based version of the SQL Server.
•Azure AppFabric
, formerly .NET Services – a collection
of services for cloud applications.

AppEngine
- a developer platform hosted on the cloud.
• Initially supported  Python, Java was added later.
• The database for code development can be accessed with
GQL (Google Query Language) with a SQL-like syntax.
•Google Co-op
- allows users to create customized search engines
based on a set of facets/categories.
•Google Drive
- an online service for data storage.
•Google Base
- allows users to load structured data from different
sources to a central repository, a very large, self-describing, semi
structured, heterogeneous database .

Gmail
- hosts Emails on Google servers and provides a web
interface to access the Email.
•Google docs
- a web-based software for building text documents,
spreadsheets and presentations.
•Google Calendar
- a browser-based scheduler;  supports multiple
user calendars, calendar sharing, event search,  display of
daily/weekly/monthly views, and so on.
•Google Groups
- allows users to host discussion forums to create
messages online or via Email.
•Picasa
- a tool to upload, share, and edit images.
•Google Maps
- web mapping service;  offers street maps, a route
planner, and an urban business locator for numerous countries
around the world

Handles automatically the deployment, capacity provisioning, load
balancing, auto-scaling, and monitoring functions.
• Interacts with other services including
EC2
,
S3
, SNS, Elastic Load
Balance and AutoScaling.
• The management functions provided by the service are:
• Deploy a new application version (or rollback to a previous
version).
• Access to the results reported by CloudWatch monitoring
service.
• Email notifications when application status changes or
application servers are added or removed.
• Access to server log files without needing to login to the
application servers.
• The service is available using: a Java platform, the  PHP server-side
description language, or the .NET framework.

CloudFront
- web service for content delivery.
•Elastic Load Balancer
- automatically distributes the
incoming  requests across multiple instances of the
application.
•Elastic Beanstalk
- handles automatically deployment,
capacity provisioning, load balancing, auto-scaling, and
application monitoring functions.
•CloudFormation
- allows the creation of a stack
describing the infrastructure for an application.

Route 53
- low-latency DNS service used to manage user’s DNS
public records.
•Elastic MapReduce (EMR)
- supports processing of large amounts of
data using a hosted Hadoop running on
EC2
.
•Simple Workflow Service (SWF)
- supports workflow management;
allows scheduling, management of dependencies, and coordination of
multiple
EC2
instances.
•ElastiCache
- enables web applications to retrieve data from a
managed in-memory caching system rather than a much slower disk-
based database.
•DynamoDB
- scalable and low-latency fully managed NoSQL
database service.

AWS Management Console -
allows users to access the services
offered by AWS .
•Elastic Cloud Computing (EC2) -
allows a user to launch a variety
of operating systems.
•Simple Queuing Service (SQS) -
allows  multiple
EC2
instances to
communicate with one another.
•Simple Storage Service (S3),Simple DB, and Elastic Bloc Storage (EBS)
- storage services.
•Cloud Watch -
supports performance monitoring.
•Auto Scaling -
supports elastic resource management.
•Virtual Private Cloud -
allows direct migration of parallel
applications .

An instance is a virtual server with a well specified set of resources
including:  CPU cycles, main memory, secondary storage,
communication and I/O bandwidth.
• The user chooses:
• The region and the availability zone where this virtual server
should be placed.
• An instance type from a limited menu of instance types.
• When launched, an instance is provided with a DNS name; this name
maps to a
• private IP address

for internal communication within the
internal EC2 communication network.
• public IP address

for communication outside the internal
Amazon network, e.g., for communication with the user that
launched the instance.

Network Address Translation (NAT) maps external IP
addresses to internal ones.
• The public IP address is assigned for the lifetime of an
instance.
• An instance can request an
elastic IP address
, rather
than a public IP address. The elastic IP address is a static
public IP address allocated to an instance from the
available pool of the availability zone.
• An elastic IP address is not released when the instance is
stopped or terminated and must be released when no
longer needed.