The Big Why ?
On January 7, 2011, Drupal 7 was released to the world with much fanfare and partying. Nearly 3 year of community collaborative coding efforts and contributions from thousands for upgrading their modules, themes, translations, distributions and much more, a fantastic platform of Drupal 7 was released to the world. But by then most of the Drupal world was accustomed to Drupal 6 and we had millions of sites powered by Drupal 6. But Drupal 7 has been here for more than year. So is the right time to shift to Drupal 7 ? Compiled from various release notes and announcements, we have got a point to point listing of why one should upgrade one’s Drupal 6 site to Drupal 7.
Drupal 7 v/s Drupal 6
Releases and Support
Drupal 6 will have only maintenance releases, which will include only major bug fixes. No new features will be added to Drupal6.
Drupal 7 is newer and hence will have longer support. Bug fixes, security fixes will be updated as soon as they are published.
Drupal 8 is currently in the early stages of development and is not yet fit for production use. A stable version (Drupal 8.0) is likely to be released in late August 2013. Once that happens, Drupal 6 will no longer be supported or receive security updates, and you will need to upgrade your Drupal 6 sites to Drupal 7 at that time.
Jquery version on Drupal 7 is by default 1.4.4, it can be upgraded to 1.5.2
Upgraded the jQuery Forms library to 2.36.
Added jQuery UI 1.8, which allows improvements to Drupal's user experience.
Drupal Commerce is available for only Drupal 7.
For complex e-commerce sites with different sales logic or sites with crowd-funding, donation, partial payment, etc. Drupal Commerce module provides flexibility of incorporating various business logic into the e-commerce feature of the website. Also due to the Drupal Commerce module built using the entity API of Drupal 7, it handles variations in products attributes in a way that is more sophisticated and in line with business practices of retailers.
More secure implementation for scheduled tasks (cron.php).
More secure password system.
More secure log-in system.
Modules can be updated via the web.
Administrative links to edit existing page elements are now available on each web page, without having to go to an administration page first.
Improved support for integration of WYSIWYG editors.
Added more drag-and-drop for administrative tasks.
Permissions now have the ability to handle more meta-data (permissions now have a description).
User 1 created as part of the installation process.
Added features to the default install profile (tagging on the Article content type).
Setting up automated task runs (cron) can now be achieved via Drupal's configuration alone, without having to install any scripts on the web server.
Redesigned password strength validator to make it kinder and gentler, and clearer.
Renamed "input formats" to "text formats".
Added support for default text formats to be assigned on a per-role basis.
Moved text format permissions to the main permissions page
Added "vertical tabs", a reusable interface component that features automatic summaries and increases usability.
Improved time zone support
Removed per-user themes: Contributed modules with similar functionality are available.
Added new "Shortcuts" module to allow user to create their own menu for the pages they visit the most.
Added query builders for INSERT, UPDATE, DELETE, MERGE, and SELECT queries.
Support for master/slave replication, transactions, multi-insert queries, delayed inserts, and other features.
Added support for the SQLite database engine.
Default to InnoDB engine, rather than MyISAM, on MySQL when available for greater scalability and data integrity.
New Drupal 7 features such as the field API, pluggable storage and cache, enables use of Mongo as a "NoSQL" solution for high performance
Database abstraction layer, enabling the use of many databases, such as Maria DB, Microsoft SQL Server, MongoDB, Oracle, MySQL, PostgreSQL, or SQLite
Several Performance Improvements Implemented
Pressflow is a fork of Drupal core with enhancements for performance, scalability, and infrastructure. Pressflow 6 made significant improvements to Drupal core in scalability and performance and most of these features have been contributed back to Drupal 7 core.
Performance and scalability improvements that serve web visitors faster via advanced caching, content delivery networks (CDN), and master-slave replication.
Hook API documentation now included in Drupal core.
Added OPML import functionality for RSS feeds.
Added feed update options.
Added support for language-aware searches.
Added test framework and tests.
Removed the Bluemarine, Chameleon and Pushbutton themes. These themes live on as contributed themes
Added "Bartik" theme as the default user interface theme.
Added "Seven" theme as the default administration interface theme.
Added "Stark" theme to make analyzing Drupal's default HTML and CSS easier.
Files are now first class Drupal objects with file_load(), file_save(), and file_validate() functions and corresponding hooks.
Files use PHP stream wrappers to enable support for both public and private files and to support pluggable storage mechanisms and access to remote resources (e.g. S3 storage or Flickr photos).
Added a field specifically for uploading files, previously provided by the contributed module FileField.
Improved image handling, including better support for add-on image libraries.
Added a field specifically for uploading images, previously provided by the contributed module ImageField.
Image operations works out of the box, operations like - resize, crop, etc.
Better support for search engine optimization and web linking
Better Support for Multisite Installations
Added RDF support
Native RDFa Semantic Web Technology in Core Drupal 7
Drupal 7 is pioneering the rollout of RDFa for broad adoption of the Semantic Web. Increasingly, Google and Bing will rely on machine-readable structured data from websites they crawl. The design of Drupal 7 embeds semantic meta data that makes machine-to-machine (M2M) search native for a Drupal 7 website. RDFa can add value by giving search engines more detail, details not visible to humans, such as the latitude and longitude of a venue for display on a map; or providing the ISO date format for localization and proper display in the search results for different countries.
Added ability to add custom fields
Provides most of the features of the former Content Construction Kit (CCK) module.
Custom data fields may be attached to nodes, users, comments and taxonomy terms.
Node bodies and teasers are now fields instead of being a hard-coded property of node objects.
Fields are translatable.
Installer can be run from the command line
Improved node access control system
Improved handling of long-running tasks.
Queue API = Batch API + Cron + ability to run batch operations over command line and on cron
The drupal project http://drupal.org/project/drupal
Choosing a Drupal Version http://drupal.org/documentation/version-info -- Drupal version nubering system explained.
What’s New in Drupal 7 http://drupal.org/about/new-in-drupal-7