Cloud Computing
(beginning with notes from Wikipedia article)

Cloud computing systems typically use REST-based APIs.
Web services often used to loosely couple components (my guess interpretation).

Multitenancy:  A single provider instance is utilitized by multiple clients.

HISTORY
    2006 Amazon offers Amazon Web Services on utility basis.
    2008 Eucalyptus offers AWS API-compatible open-source platform for private
     clouds.

LAYERS
    Client
    Application.  SaaS.
    Platform.  PaaS = Platform as a Service.
    Infrastructure.  IaaS = Infrastructure as a Service
         Like raw block storage and networking.
         Often virtualized.
         Usually metered.
    Server.  Actual hardware and software components particularly designed or
     suited to Cloud operation.
    [Sometimes NaaS, Network as a service]

Private clouds may be internally or externally hosted.
Virtual Private Cloud = private cloud assembled from public cloud resources.


Public Services
    Amazon AWS = Amazon Web Services.  Amazon'd cloud computing platform
        Amazon EC2 = Elastic Compute Cloud.  IaaS.
            Virtual private servers using Xen
            See separate file $HOME/doc/java/ec2.txt
        Amazon S3 = Simple Storage Service
            Provides storage through web service interfaces:
              REST, SOAP, BitTorrent
            Recently allow to host entire website.
            Like GAE can't do bare domain, but can do arbitrary subdomain.
            The Xen images canmount an S3 bucket as a FS using FUSE, incl.
             Hadoop FS.
            Many serivces, incl. Dropbox, use S3 for storage and transfer.
    Google App Engine = GAE = GAE/J.  PaaS.
        Very dummied-down and restricted compared to EC2.
        GAE Java servlet container uses Jetty Web Server
        gae-filestore.  Virtual FS.
        Only a subset of JRE may be used:  "The JRE Class White List"
        Can only execute upon http requests.
        Cannot create new threads.
        SSL/HTTPS domain restriction.
        Only www.domain.name supported, not bare 'domain.name.'  Dumb.
        Dummied down non-relation SQL alternative named GQL.
        As of 10/2011, offer MySql option.
    vCloud (by VMware)
    OpenStack (by Rackspace Cloud and NASA)
    Azure Services Platform.  Microsoft in MS data centers.