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作者 wpadmin 的所有文章
Cloud applications
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.
PaaS and SaaS services from Microsoft
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.
PaaS services offered by Google
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 .
SaaS services offered by Google
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