Page 107 - Cloud Computing (Elective – III)

Differences between SQL and GQL

Google App Engine’s datastore has a SQL-like syntax called “GQL”. GQL
intentionally does not support the Join statement, because it seems to be
inefficient when queries span more than one machine. Instead, one-to-many and
many-to-many relationships can be accomplished using ReferenceProperty().
This shared-nothing approach allows disks to fail without the system failing.
Switching from a relational database to the Datastore requires a paradigm shift
for developers when modelling their data.

Unlike a relational database the Datastore API is not relational in the SQL sense.
The Java version supports asynchronous non-blocking queries using the Twig
Object Datastore interface. This offers an alternative to using threads for parallel
data processing.

Open-Source Cloud

An open-source cloud is designed and developed using open-source technologies
and software such as:
 Open-source operating system, DBMS and software development
frameworks
 Open-source workflow and business applications
 Virtualization stack (Hypervisor, virtualization management)
 Hardware with open-source firmware

Moreover, open-source cloud may also refer to any cloud service that provides
open-source software or service to end users or businesses. Businesses/cloud
providers have the option to customize open-source cloud solutions to a greater
extent, which is generally prohibited in closed-source cloud models. Open-source
cloud solutions generally are interoperable with any back-end platform and can
easily be migrated to a different IT infrastructure/environment.
Open Nebula, Open Stack and Virtual Box are common examples of open-source
cloud.