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How much RAM should you get with your dedicated server?

Good question! We almost always encounter this question, especially for those clients who are moving from a traditional shared web hosting environment, or VPS, to their own dedicated server. We also see this question when clients are upgrading to a newer platform from a dated dedicated server setup (3 years and older). This question is not easily answered without addressing all of the variables which will consume RAM on the new server. Let's take a look at the major ones.

1) Operating System - It is important to know how much RAM your operating systems requires to run smoothly and efficiently. In their specifications, operating system developers issue a minimum RAM requirement and a recommended minimum RAM requirement. For example, Windows Server 2003 specifies a minimum RAM of 512MB and a recommended minimum of 1GB in their Datacenter Edition. In the case of CentOS 6, the recommended stated minimum is 512MB but almost every server technician recommends 1GB.

Oddly enough, when selecting your operating system for your dedicated server, you must also be aware of the maximum RAM allowed by the license of your operating server edition. This is most relevant when it comes to Windows where the Standard Edition License typically caps RAM usage at 4GB (2003, 2008). Windows Home Server 2011, also called Vail, requires 2GB minimum, and allows for 8GB maximum. With Linux versions such as CentOS 6, RAM limits are much larger, 2TB maximum, and rarely an issue.

2) Control Panel - If you are planning to use a control panel such as cPanel or Plesk on your dedicated server, be aware it too requires a minimum and recommended amount of RAM. cPanel states that they require a minimum of 256MB of RAM; however, most practical applications require 1 to 2GB's. Other panels such as Helm are RAM gluttons, requiring a minimum of 1GB of RAM simply to function.

3) Other Applications - Depending on your intended use, it is helpful to make a "laundry list" of other applications you intend to run on your dedicated server. For example, it is very common to run Apache Web Server which requires a minimum of 256MB of RAM but will function most efficiently at 1GB. Other applications may include email clients, hypervisor, antivirus, and spam prevention, each with their own minimum RAM requirements.

4) Site Traffic and Usage - The more traffic that comes to your website, the more page views and data serving requirements you will have. As a rule of thumb, for most standard websites, we recommend 1GB of RAM for every 2500 visitors per day. Skew this rule appropriately if your website pages are large and/or the data being served is intensive.

5) Website Characteristics and Caching - Depending on how your website has been designed you must be aware of how static or dynamic your website is. If scripting languages such as Perl and PHP are being used, be aware your requirement for RAM will jump dramatically, but a RAM increase could also be your solution to faster page speed load times. In addition, when using databases such as MySQL and PostgreSQL, be advised that these are regarded as "memory pigs" and the larger the database, the more RAM you will need. It is also important to evaluate how much of your website is static content which can be cached by proxy servers and users browsers. The more images, CSS Sprites and Javascript you cache and compress, the less RAM you will be reliant on. Evaluating the optimization abilities of your web designer will help determine this. You may get some indication by visiting Google's PageSpeed Insights which will evaluate and generate a PageSpeed report with Insights. The link is listed below.

https://developers.google.com/speed/pagespeed/insights

These are the most important variables to determine how much RAM you need and can be summarized by the following formula:

OS + CP + OA + Traffic + WS = TOTAL REQUIREMENTS.

A well designed website with 5000 daily visitors running CentOS6, cPanel, Apache Web Server, and a small MySQL database may look as follows:

1GB + 2GB + 1GB + 2GB + 1GB = 7GB

In this example, our sample configuration should require about 7GB of RAM. Given that RAM DIMMS are often "paired", the client would likely be required to order either 6GB or 8GB of RAM. We are great believers that more RAM is always better; hence we would recommend 8GB as the starting point in this example.

Remember, this formula is only the beginning in evaluating your servers RAM needs. Once your applications are up and running it is import to test your applications for speed and load times, and also examine your server statistics to determine if you accurately estimated RAM consumption.