Hier ein Auszug von modrails.com
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Phusion Passenger™ — a.k.a. mod_rails or mod_rack — makes deployment of Ruby web applications, such as those built on the revolutionary Ruby on Rails web framework, a breeze. It follows the usual Ruby on Rails conventions, such as “Don’t-Repeat-Yourself”.
•Deployment is only a matter of uploading application files. No Ruby (on Rails)-specific server configuration required!
•Supports both the industry standard Apache web server and the fast and lightweight Nginx web server.
•Allows Ruby on Rails applications to use about 33% less memory, when used in combination with Ruby Enterprise Edition (optional).
•Zero maintenance. No port management, server process monitoring or stale file cleanup required. Errors are automatically recovered whenever possible.
•Designed for performance, stability and security. Phusion Passenger should never crash Apache even in case of crashing Rails applications.
•Well-documented, for both system administrators and developers!