Scaling-out WordPress – Performance Measures – CPU and RAM influence on the fronts

 CPU & RAM influence

Results overview

Raw throughput of a WordPress web site and influence of cpu and memory on the front

In order to evaluate the expected performance of a WordPress web site, I first decided to focus on a single front and to play with the CPU and MEMORY resources of the front.

To be sure that no other bottlenecks appear (such as the database server resources  -CPU, MEMORY, IO – or the network resources), I was continually checking the performance counters on the database server and on the front server with commands such as iostat, vmstattop and iftop for the network during the workload. After a while, I found the perfect command dstat that shows all counters for CPU, IO and MEMORY from just one command line.

To quickly evaluate the speed (throughput) of the web site, I decided to use the apache tool ab that gives a very useful indicator in req/s.
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Scaling-out WordPress – Introduction

This post is the first one of a series about scaling out WordPress.


The purpose of this series of posts can be summarized as followed:

  • Experiment the different bricks (load-balancer haproxy, mysql replica, session sharing)
  • What kind of performance increase we can expect ? Is the performance increase linear with the number of web fronts?
  • What will be the bottlenecks ?
  • What kind of tools can we easily use to stress the application ?
  • What kind of tools can we easily use to measure the performance metrics  ?


Software installation
Performance Measures

to come :
Sessions sharing
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