Understanding memory consumption is crucial for maintaining high-performing Drupal 7 websites. Let's explore how different types of websites handle memory differently and learn strategies for optimizing performance.

Understanding Website Categories

Drupal websites generally fall into two main categories regarding memory consumption:

1. Anonymous browsing websites: Sites where most users view content without logging in
2. Authenticated access websites: Platforms requiring users to log in to access content or perform actions

Memory Consumption Analysis

A typical Drupal 7 request to the Apache server consumes significant memory, typically ranging from 30 to 60 MB per request. In some cases, this can increase to 90 MB, depending on the activated modules. This substantial memory usage stems from two primary factors:

1. Bootstrap Procedure Memory: Drupal's bootstrap process loads all enabled modules during each request, consuming considerable memory.

2. Block Rendering Memory: Each block on a page requires additional memory resources. This becomes particularly significant in AJAX-enabled websites, where blocks load separately. When a user opens such a page, the memory usage multiplies based on the number of AJAX calls required to load individual elements.

Optimization Strategies for Anonymous Traffic

For websites primarily serving anonymous users, implementing caching solutions provides significant benefits. Consider implementing:

- Boost module: Creates static HTML copies of your pages
- Varnish: Provides advanced caching capabilities
- Proper .htaccess configuration: Ensures static files are served directly rather than regenerating pages

These caching solutions create static copies of your pages, allowing your server to handle numerous requests with minimal memory overhead.

Managing Authenticated User Traffic

For websites serving primarily authenticated users, available memory and server performance become critical limiting factors. Let's consider a practical example:

On a server with 4 GB of memory:
- Operating system reserves approximately 700-800 MB
- Leaving approximately 3.2 GB for Drupal requests
- With 50 MB per request, theoretical maximum is 64 concurrent requests
- Real-world performance typically allows 100-150 concurrent logged-in users

Performance Optimization Techniques

To improve performance and reduce memory consumption:

1. Module Optimization:
  - Audit and remove unnecessary modules
  - Identify and replace memory-intensive modules
  - Consider custom development for inefficient functionality

2. Server Configuration:
  - Implement NGINX to manage server load
  - Configure eAccelerator for PHP optimization
  - Use FastCGI (FCGI) with Apache for better performance
  - Ensure adequate memory caching configuration
  - Verify storage system performance (SSD recommended)

3. Memory Management:
  - Monitor memory usage patterns
  - Implement memory limits per PHP process
  - Configure optimal PHP memory settings

Important Considerations

Remember that memory consumption isn't static - it varies based on:
- The complexity of your site's functionality
- The number of enabled modules
- The type of content being served
- User interactions and permissions
- Server configuration and capabilities

Regular monitoring and optimization of these factors ensures optimal performance and stability of your Drupal 7 website.

Understanding these concepts and implementing appropriate solutions based on your website's specific needs will help maintain performance and reliability as your site grows. Regular performance audits and adjustments ensure your website continues to meet user demands efficiently.