I have had a cloud server with 8 Core and 8 GB RAM and only got less than 15 sites added on that VestaCP server. I thought everything was ok. But day after doing this I found all of my site showing an error in header including WordPress sites. The error was “Unable to allocate memory pool”. I started searching why this is happening! Thought it could be server problem for virtual memory because they didn’t mentioned “Guaranteed RAM”. After lot of search I failed to achieve any result how to solve this. Then I decided to change server. I bought a dedicated server and installed all same thing like that cloud server, I found the result is same. That error still occurring. Then I started serious analyzing to overcome this problem cause I like to use vestacp but if this remain unsolved I must leave it!
At last I have got the solution! It is for APC (Alternative PHP Cache) installed by vestacp. This thing is very good for your server and page speed. So what to do now?
In /etc/php.d/apc.ini I have just edited one thing that is
I have changed it like
You can increase it as per your need. Don’t increase much if you have not much memory available in your server.