RAM/CPU calculations when using PHP-FPM and Apache 2.4

["Rose, John B" <jbrose@xxxxxxx>]

Is this the correct process?

To determine how much RAM/CPU to provide for a VM web server, calculate the average RES value in "top" for httpd processes. Then calculate the average RES value for php-fpm processes. Then add those 2 values together. Then multiply by the max number of concurrent connections you want to be able to handle.

Example:

12000 kb 

  6640 kb

------------

18.640 mb

   X 512 MaxRequestWorkers

----------------

~9.6 gb  (How much RAM needed to run apache/PHP-FPM. So would add 2 GB for running system)

Then add the average CPU% in "top" for httpd processes + average CPU% for php-fpm and multiply by 512 MaxRequestWorkers.

Example:

Httpd average cpu 4%

Php-fpm average cpu  2%

.06 x 512 = 30.72 cores

The RAM looks reasonable. But the cpu value is much higher than I expected. 

Corrections? Constructive comments? 

Thanks