According to Jacob Nielsen, the usability guru for web based applications, the page load time of websites should stay below 1 second to make a website "feel fast" (see: Response Times: The 3 Important Limits, an excerpt of his book "Usability Engineering").
Of course this rule also applies to PRTG's web interface. As long as you stay below 1,000-2,000 sensors you will get page load times below 1 second on most systems. Even our super-slow netbook test installation of PRTG with 1,400 sensors (running on an Atom based DELL Inspirion Mini netbook) achieves an average page load time below 500ms.
But when your PRTG installation has several thousand sensors you can run into slow page loads even when PRTG runs on high performance hardware. Some pages of the web interface are especially problematic as far as this is concerned: Unfiltered sensor lists, log data tables, top 10 lists.
It is completely normal that a PRTG installation becomes slower with an increasing number of sensors, in fact page load times are becoming linearly slower with the number of sensors. But there are still various things that you can do to speed up PRTG. In this blog article I want to compile a list of actions you can take!
By the way, there is also an extensive knowledge base article with many more tips: How can I speed up PRTG - especially for large installations?
The measurements mentioned in this article were all created using PRTG's built-in web page speedtest. We used the following test systems:
| "AMD Barebone" | Barebone Server | AMD Athlon II X4 640 Processor @ 3 Ghz Win2k8R2, 4 Cores | 4,000 Sensors |
| "8 Core Poweredge" | DELL Poweredge Server 2950 | Intel Xeon X3450 Dual Processor @ 2.67 Ghz Win2k8R2, 8 Cores | 6,000 Sensors |
| "4 Core Poweredge" | DELL Poweredge Server 2850 | Intel Xeon E5405 Dual Processor @ 2 Ghz Win2k8R2, 4 Cores | 1,200 sensors |
| "Dual Core Optiplex" | DELL Optiplex 980 | Intel Core i5 750 Processor @ 2.67 Ghz Win2k8R2, 2 Cores | 4,000 sensors |
We frequently release performance improvements with new versions of PRTG. For example when you update from version 8.3.2 to version 8.3.3 you will get 30%-75% quicker page load times. During testing we recently found out that on Windows 2008 a specific string management function that is used extensively in the PRTG code (e.g. to create the HTML output of the web server) is much slower than on Windows 2003. We optimized the code to work around this effect. The web interface is now up to 73% faster on Windows 2008 R2. Simply install the latest version 8.3.3 and you will see page load times reduced by 50%-70% (note: On Windows 2003 times are only about 30% better).
Sample real-world measurements of average web page load times:
| AMD Barebone | lowered from 948 ms to 408 ms | 57% better |
| 8 Core Poweredge | lowered from 412 ms to 211 ms | 49% better |
| 4 Core Poweredge | lowered from 361 ms to 101 ms | 73% better |
| Dual Core Optiplex | lowered from 822 ms to 283 ms | 66% better |
This setting, introduced in V8.2, can be found under the Website Settings. It disables some features to improve web page times. This leads to faster web page creation.
Sample real world measurements of average web page load times:
| AMD Barebone | lowered from 948 ms to 527 ms | 55% better |
| 8 Core Poweredge | lowered from 108 ms to 77 ms | 29% better |
| 4 Core Poweredge | lowered from 317 ms to 212 ms | 34% better |
On Windows 2008 the power plan “Balanced” is the default setting. If your CPU supports “Processor Power Management” and if the feature is enabled in the system BIOS you may experience a major performance impact on PRTG. Switching to the “High Performance” power plan can lower you average web page times by 30-50%.
Our observation was that the effect is even stronger when the processor has many cores. There is a knowledgebase article on the Microsoft website about this, quote: “If your server requires low latency, [..] you might not want the processors switching to lower-performance states.”
Sample real world measurements of average web page load times:
| AMD Barebone | lowered from 408 ms to 246 ms | 40% better |
| 8 Core Poweredge | lowered from 211 ms to 108 ms | 49% better |
| Dual Core Optiplex | lowered from 283 ms to 190 ms | 33% better |
A few months ago we found during in-house testing that it makes a difference when we run the PRTG core server on Windows 2008 R2 or on Windows 2003 R2 (both 64 bit). Web pages of a core server installation on Windows 2008 R2 take longer to generate than web pages for the same monitoring configuration on the same hardware on Windows 2003 R2 64bit. For small installations (<500 sensors) the slowdown is barely noticeable, but with a few thousand sensors the latency of the web interface becomes more and more annoying.
We researched this problem extensively. We created and ran numerous performance tests. We applied various optimizations and rewrote some code sections. We even purchased several dedicated test servers to find the cause for this issue. All this work already resulted in major speed improvements for PRTG: Based on our results we already released several speed improvements in January and February with version 8.3.1, version 8.3.2, and now once more with version 8.3.3 (see "Action 1" above). But still a performance gap between Windows 2003 and 2008 is unsolved.
Even after all improvements PRTG is still 20-30% faster on Windows 2003 when compared to Windows 2008 (128ms vs. 190ms average page load time on our AMD barebones). The reason remains unknown for the time being. Nevertheless you can make use of this fact by using Windows 2003 R2 64bit for your monitoring engine to make it faster.
We have not yet extensively tested this, but early measurements show that using an SSD disk in a PRTG server can lead to 25-35% faster page load times compared to a normal disk drive.
If you can successfully combine all four methods you can reduce page load times by more than 80%.
Sample real world measurements of average web page load times:
| AMD Barebone | lowered from 948 ms to 169 ms | 83% better |
| 8 Core Poweredge | lowered from 412 ms to 77 ms | 82% better |
| 4 Core Poweredge | lowered from 129 ms to 39 ms | 74% better |
| Dual Core Optiplex | lowered from 822 ms to 190 ms | 77% better |
If we add these recent improvements on top of what we have already released in recent weeks then your PRTG web interface today can run 10-30 times faster than the initial version 8 release in September 2010.