11 Practical Tips to Effortlessly Boost Apache Performance on CentOS

Boost Apache Performance on CentOS

Apache HTTP Server is one of the most popular and widely used open-source web servers globally. It’s renowned for its power, flexibility, and robustness, which has made it a prime choice for hosting websites. However, like any software, Apache’s performance can be significantly improved with the right configuration and optimization techniques.

This tutorial provides 11 beginner-friendly tips to boost the performance of Apache on CentOS, a popular Linux distribution often used in server environments.

Before we dive into the details, it’s important to understand the basics of Apache and CentOS. Apache is a software that serves web content to users. It’s capable of serving static content, like HTML pages and images, as well as dynamic content generated by server-side scripts. CentOS, on the other hand, is a free and open-source operating system derived from the sources of Red Hat Enterprise Linux (RHEL). It’s widely used in server environments due to its stability and long-term support.

For a more in-depth understanding of Apache, you can refer to our article on Apache.

If you’re interested in exploring other web server options, you might find our guide on the best web servers useful.

Now, let’s move on to the tips to optimize Apache on CentOS.

Tip 1. Update Apache and CentOS

The first and foremost tip is to keep your Apache and CentOS up-to-date. Updates often come with performance improvements, security patches, and new features that can enhance the overall performance of your server. To update Apache and CentOS, use the following commands:

sudo yum update httpd
sudo yum update

Tip 2. Enable KeepAlive

KeepAlive, also known as persistent connection, is an essential feature in the Apache HTTP Server that significantly enhances its performance. It allows multiple requests from a client to be served over a single HTTP connection, rather than opening a new connection for each request.

To understand the importance of KeepAlive, let’s consider a scenario where a user visits a webpage that contains several elements like images, CSS, and JavaScript files. Without KeepAlive, each of these elements would require a separate HTTP connection to be served. This means that for a single webpage, the server might need to open and close hundreds of connections, which can be a resource-intensive process and can significantly slow down the server.

However, with KeepAlive enabled, all these elements can be served over a single, persistent HTTP connection. This reduces the overhead of opening and closing multiple connections, leading to faster page load times and a better user experience. It also reduces the CPU usage and the network latency, making your server more efficient.

To enable KeepAlive in Apache, you need to locate the main configuration file, ‘httpd.conf’. This file is usually located in the ‘/etc/httpd/’ directory on CentOS. Once you’ve opened the file, look for the ‘KeepAlive’ directive. If it’s set to ‘Off’, change it to ‘On’. If the directive doesn’t exist, you can add it to the file.

Here’s how it should look:

KeepAlive On

After making the change, save the ‘httpd.conf’ file and restart the Apache server for the changes to take effect.

You can do this by using the following command:

sudo systemctl restart httpd

Remember, while KeepAlive can significantly improve your server’s performance, it’s important to monitor your server to ensure it’s not keeping too many connections open for too long, as this can also consume resources. You can adjust the ‘KeepAliveTimeout’ directive in the ‘httpd.conf’ file to control how long the server waits for new requests on a persistent connection.

Tip 3. Optimize ‘MaxClients’ and ‘MinSpareServers’

The ‘MaxClients’ and ‘MinSpareServers’ directives in Apache’s configuration are crucial parameters that can significantly impact your server’s performance. They control the number of simultaneous connections that your server can handle and the minimum number of idle child server processes, respectively.

The ‘MaxClients’ directive sets the limit for the maximum number of simultaneous requests that can be served. Each client connecting to your server starts a separate process or thread, and ‘MaxClients’ determines how many of these processes or threads Apache is allowed to start.

For example, if you set ‘MaxClients’ to 150, as in the code snippet below, Apache will only serve 150 requests at the same time. Any additional requests will be queued and will have to wait for an existing connection to close before they can be served.

MaxClients 150

Setting this value too low could lead to a slower website, as Apache may not be able to serve all incoming requests, especially during peak traffic times. On the other hand, if ‘MaxClients’ is set too high, Apache may consume too much of your server’s resources, such as memory and CPU, which could lead to server instability or even crashes.

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The ‘MinSpareServers’ directive, on the other hand, determines the minimum number of idle child server processes. These are processes that are started but not currently serving any requests. They are kept spare so that when a new request comes in, Apache doesn’t have to start a new process, which can be resource-intensive, but can instead use one of the spare ones.

MinSpareServers 20

In the example above, Apache is configured to keep at least 20 server processes idle. If the number of idle processes falls below this number, Apache will start more processes to compensate. This can help to ensure that there are always enough processes ready to serve incoming requests, improving response times.

However, just like with ‘MaxClients’, setting ‘MinSpareServers’ too high can consume unnecessary resources, as Apache will keep more processes running idle than necessary. Conversely, setting it too low could lead to slower response times, as Apache may need to frequently start new processes to serve incoming requests.

In conclusion, optimizing ‘MaxClients’ and ‘MinSpareServers’ involves finding a balance that suits your server’s resources and your website’s traffic patterns. It’s recommended to monitor your server’s performance and adjust these values as necessary to ensure optimal performance.

Tip 4. Use a Content Delivery Network (CDN)

A CDN is a geographically distributed network of proxy servers and their data centers. The primary goal of a CDN is to provide high availability and performance by distributing the service spatially relative to end-users. CDNs are used to relay web content, including HTML pages, javascript files, stylesheets, images, and videos.

When a user visits your website, the CDN redirects the request from the originating site’s server to a server in the CDN that is closest to the user and delivers the cached content. This process is nearly invisible to the user. The only way a user would know if a CDN has been accessed is if the delivered URL is different than the URL that has been requested.

For example, let’s say your Apache server is located in New York, and a user from London accesses your website. Without a CDN, the user’s request has to travel across the Atlantic, to your server in New York, and then back again with the requested data. This can result in noticeable latency, which can affect the user’s experience.

However, if you’re using a CDN, the user’s request would be redirected to a CDN server closer to them, perhaps one located in London itself. This server would then deliver the cached content from your website, significantly reducing latency and improving the speed and performance of your website for that user.

By using a CDN, you can not only improve your website’s speed and performance but also reduce the load on your Apache server. This is because a significant portion of user requests and data delivery is handled by the CDN, leaving your Apache server with more resources to process dynamic content and other tasks.

In addition to improving website performance, CDNs also provide other benefits such as reducing bandwidth costs, increasing content availability and redundancy, and improving website security by providing DDoS mitigation and improvements to security certificates.

Therefore, using a CDN can be a powerful way to boost the performance of Apache on CentOS, especially for websites that serve a global audience or have high traffic volumes.

Here are some suggestions for CDNs that you can consider:

Paid CDNs

  • Fastly is a highly configurable CDN known for its low latency and high-speed data transfer. It’s used by many high-traffic websites, including The New York Times and GitHub.
  • StackPath offers a secure CDN with built-in WAF, DDoS protection, and edge computing capabilities. It’s a good choice for businesses looking for a CDN with strong security features.

Free CDNs

  • Cloudflare offers a free CDN plan that includes some of their security and performance features. It’s a good choice for small websites and blogs.
  • Jetpack offers a free CDN for images and static files as part of their plugin if you’re running a WordPress website. This can help speed up your website without any additional cost.

Tip 5. Enable GZIP Compression

GZIP compression reduces the size of the data that Apache sends to clients, which can significantly speed up your website.

To enable GZIP compression, add the following lines to your ‘.htaccess’ file:

AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE application/x-javascript

Tip 6. Disable Unnecessary Apache Modules

Apache HTTP Server is a highly modular system. It comes with a wide array of modules that extend its functionality, allowing it to handle tasks like URL rewriting, SSL encryption, proxying, and more. While this modularity makes Apache incredibly versatile, it also means that your server might be running modules that it doesn’t need, which can consume valuable system resources and slow down your server’s performance.

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For instance, if your website doesn’t use CGI scripts, there’s no need to have the mod_cgi module enabled. Similarly, if you’re not using any server-side includes, the mod_include module is unnecessary. Each of these modules, when enabled, consumes memory and CPU cycles, even if they’re not being used.

To optimize your Apache server, it’s a good practice to review the list of enabled modules and disable those that aren’t needed. In CentOS, the list of enabled modules can be found in the ‘/etc/httpd/conf.modules.d/’ directory. Each file in this directory corresponds to a module, and by renaming or removing these files, you can disable the corresponding modules.

However, a more straightforward way to disable modules is to use the ‘a2dismod’ command, followed by the name of the module you want to disable.

For example, to disable the mod_cgi module, you would use the following command:

sudo a2dismod cgi

After running this command, you’ll need to restart Apache for the changes to take effect:

sudo systemctl restart httpd

Remember, before disabling a module, make sure that it’s not needed by your website or any of its components. Disabling a necessary module could lead to errors or even make your website inaccessible. Always test your website thoroughly after making changes to your server’s configuration.

By disabling unnecessary Apache modules, you can free up system resources and improve your server’s performance, making your website faster and more responsive for your users.

Tip 7. Use Expires Headers

Expires headers tell the browser whether it should request a specific file from the server or fetch it from the browser’s cache. By using expires headers, you can reduce the load on your server and improve page load times.

Add the following lines to your ‘.htaccess’ file to enable expires headers:

<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType image/jpg "access plus 1 year"
ExpiresByType image/jpeg "access plus 1 year"
ExpiresByType image/gif "access plus 1 year"
ExpiresByType image/png "access plus 1 year"
ExpiresByType text/css "access plus 1 month"
ExpiresByType application/pdf "access plus 1 month"
ExpiresByType text/x-javascript "access plus 1 month"
ExpiresByType application/x-shockwave-flash "access plus 1 month"
ExpiresByType image/x-icon "access plus 1 year"
ExpiresDefault "access plus 2 days"

Tip 8. Optimize .htaccess

The .htaccess file is a powerful tool that allows you to change server configuration on a per-directory basis. However, for each request, Apache looks for and reads the .htaccess file, which can slow down your website.

If you have access to the main server configuration file (usually called ‘httpd.conf’), consider moving the .htaccess content into it and then disable .htaccess.

# Disable .htaccess
AllowOverride None

Tip 9. Use a Static Content Server

Static content, such as images, CSS files, and JavaScript files, forms a significant part of most websites. These files don’t change often and don’t require server-side processing, making them ideal candidates for serving from a separate, dedicated server. This approach is known as using a static content server.

The primary advantage of using a static content server is that it offloads the task of serving static files from your main Apache server. This reduces the load on your Apache server, freeing up resources for it to process dynamic content more efficiently, such as PHP scripts or database queries.

For example, let’s say your website has a large image gallery. Each time a user visits the gallery, your server has to serve potentially hundreds of images. If all these requests are handled by your main Apache server, it can quickly become overwhelmed, especially if there are many concurrent users. This can lead to slower response times and a poor user experience.

However, if you use a separate static content server to serve the images, your main Apache server is free to focus on processing dynamic content. The static content server can be optimized specifically for serving static files, allowing it to deliver the images quickly and efficiently. This results in faster page load times and a smoother user experience.

To implement a static content server, you can use a subdomain (like static.yourwebsite.com) and configure it to point to a separate server. You then update your website’s code to reference this subdomain for static files. For example, an image that was previously served from “www.website.com/images/logo.jpg” would now be served from “static.website.com/images/logo.jpg”.

Remember, the static content server doesn’t have to be a physical server. It can be a virtual server or even a service provided by a third-party company, such as a CDN. The key is that it’s separate from your main Apache server and is optimized for serving static content.

By using a static content server, you can significantly improve the performance of your website, especially if it serves a lot of static content. It’s a relatively simple change that can have a big impact on your website’s speed and user experience.

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Tip 10. Use the Latest PHP Version

If your website uses PHP, make sure you’re using the latest version. Each new version of PHP comes with improvements and optimizations that can significantly boost your website’s performance.

To update PHP on CentOS, use the following command:

sudo yum update php

Tip 11. Monitor Your Server

Monitoring your server’s performance is a critical aspect of maintaining a high-performing, reliable web server. Regular monitoring allows you to keep an eye on various metrics and parameters that can directly impact your server’s performance and, consequently, your website’s user experience.

Monitoring can help you identify any issues early, such as sudden spikes in traffic, resource bottlenecks, or hardware failures. By catching these issues early, you can take corrective action before they escalate and affect your website’s performance or, worse, cause downtime.

There are several tools available that can aid in server monitoring. Here are a few examples:

  1. top: This is a real-time command-line tool in Linux that provides a dynamic, real-time view of the processes running on a system. It displays information about CPU usage, memory usage, load average, and other system details. This can help you identify processes that are consuming excessive resources.
  1. htop: This is an interactive process viewer for Unix systems, similar to ‘top’, but with a more user-friendly interface. It provides a full list of processes running, along with details like user, CPU usage, memory usage, and process ID. It also allows you to kill processes directly from the interface.
  1. apachetop: This is a very useful tool for monitoring Apache logs in real-time. It displays the number of requests per second, the most visited URLs, and other useful information. This can help you identify patterns or anomalies in your web traffic that could indicate a problem.
apachetop -f /var/log/httpd/access_log

Remember, the key to effective server monitoring is regularity. Set up a schedule to check your server’s performance regularly, and consider using automated monitoring tools that can alert you to potential issues. This proactive approach can save you a lot of trouble in the long run and ensure your server continues to deliver optimal performance.

Commands Mentioned

  • sudo yum update httpd – Updates Apache
  • sudo yum update – Updates CentOS
  • sudo a2dismod [module_name] –Disables an Apache module
  • sudo yum update php – Updates PHP

FAQ Section

  1. What is the impact of KeepAlive on Apache’s performance?

    KeepAlive allows multiple requests from a client to be served over a single HTTP connection. This reduces the overhead of establishing a new connection for each request, thereby improving server performance and response times.

  2. How does GZIP compression improve website speed?

    GZIP compression reduces the size of the data that Apache sends to clients. This results in faster data transfer times, leading to quicker page load times and a better user experience.

  3. Why should I disable unnecessary Apache modules?

    Each enabled Apache module consumes resources. By disabling modules that aren’t necessary for your website, you can free up resources and improve Apache’s performance.

  4. What is the benefit of using a CDN?

    A CDN reduces the load on your Apache server by delivering web content to users based on their geographic location. This can improve your website’s speed and performance, especially for users who are far from your server’s location.

  5. Why is it important to monitor server performance?

    Regularly monitoring your server’s performance helps you identify any issues early and take corrective action before they affect your website’s performance. It provides valuable insights into resource usage, traffic patterns, and potential bottlenecks.


Boosting the performance of Apache on CentOS involves a combination of updating and configuring the software, optimizing content delivery, and regularly monitoring server performance. By implementing the tips provided in this guide, you can significantly enhance your server’s efficiency, speed, and reliability, leading to a better user experience for your website’s visitors.

Remember, every server environment is unique, and what works best for one might not work as well for another. Therefore, it’s crucial to thoroughly test any changes you make to ensure they’re beneficial for your specific situation.

For more information on different server types, you can check out our articles on dedicated server hosting, VPS hosting, cloud hosting, and shared hosting. If you’re interested in exploring other web server options, you might find our guide on Nginx and LiteSpeed useful.

Remember, the key to a high-performing server lies not just in its configuration, but also in its maintenance. Regular updates, monitoring, and optimizations are crucial to ensuring your server continues to deliver the best performance possible.

Happy hosting!


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