This software is a variant of Drupal that includes improvements for better functionality, scalability, and testing.
To overcome this hurdle, Pressflow brings together the most popular enhancements to the Drupal core into a single deployable package. These enhancements have been tested thoroughly by the experienced Four Kitchens team before release. Pressflow is a free, open-source software just like Drupal, released under the GNU General Public License. It leverages the success of an existing popular open-source, free software package with enhancements geared towards a specific user group.
Pressflow releases align with Drupal core releases and maintain compatibility with modules and themes. After each Drupal core release, Pressflow undergoes a review, and all enhancements are reset. It ensures that any new major Drupal release that incorporates the enhancements previously exclusive to Pressflow can utilize the standard Drupal implementation. Older major versions of Pressflow continue to support the Pressflow-exclusive implementations.
One of the characteristics that make Pressflow scale is its support for database replication. Pressflow can use replicated MySQL servers, which are currently in use on Drupal.org and many other large Drupal sites, to handle time-consuming query operations that would slow down the central database. Unlike standard Drupal releases, Pressflow supports replication for seamless scaling.
Another feature that sets Pressflow apart is its support for Squid and Varnish reverse proxy caching. This support takes most of the load of anonymous browsing off of Drupal, PHP, Apache, and MySQL by placing a high-performance cache in front of the web application stack. Squid and Varnish are the most popular open-source reverse proxy caches that can deliver high-traffic sites, such as Wikipedia. Pressflow facilitates effective reverse proxy cache deployment by allowing the content management system to inform the cache what it can and cannot cache- a capability only available in Pressflow.
Pressflow streamlines optimizations for MySQL, which exceeds Drupal's broad storage support for MySQL, PostgreSQL, and SQLite. Many large Drupal sites use MySQL, which enables Pressflow to integrate optimizations quickly. It also optimizes for PHP 5, removing the need for wrapper functions that slow down Drupal on PHP 4. Replacement with high-performance PHP 5 equivalents in Pressflow speeds up code and resolves wrapper function-related issues.
Overall, Pressflow is an excellent enhancement to Drupal for high-traffic sites. With increased performance, scalability, and data integrity, Pressflow is worth considering for businesses that have outgrown the standard Drupal platform.
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