PHP/FCGI balancing

Igor Sysoev is at
Wed Jun 18 14:32:04 MSD 2008

On Wed, Jun 18, 2008 at 09:51:02AM +0100, Phillip B Oldham wrote:

> Igor Clark wrote:
> >I'm considering whether to:
> >
> >- leave all web serving to 8GB box 1, and dedicate 8GB box 2 to PHP 
> >application serving, or
> >
> >- load-balance web traffic between both 8GB boxes, say 70% to existing 
> >box and 30% to new box, and run PHP app server on new 8GB box.
> >
> >As per Q1, I'd like to be able to specify some weighting on the 
> >fastcgi-->PHP traffic so that I could tune which box processes what a 
> >bit more finely, but from what I can see in the nginx documentation, 
> >this isn't possible.
> >
> >The latter way seems to spread the load, but the former way dedicates 
> >machines to doing one thing at a time. Given that the nginx box is 
> >currently running at loads of less than 0.1 and has over 2GB of RAM 
> >free, perhaps the extra nginx muscle isn't necessary.
> >
> >There is a bit of processing overhead on the PHP side, as the AMF 
> >codec processing has to be done in PHP (the PHP AMF C extension has a 
> >bug with AMF3 which breaks our app) - although we're using APC, which 
> >seems to speed things up nicely.
> >
> >What do you think would be most sensible?
> Would it not be better to use the two 8's for MySQL and PHP (same set-up 
> on both, with the mysql db replicating from one to the other), and have 
> the two 4's as nginx servers in a fail-over scenario? I'd've thought 
> that nginx wouldn't benefit as much from the ram as PHP & MySQL would, 
> and ensuring that if one of the "app" servers goes down its not the end 
> of the world as you can still serve content.

nginx itself does not require much memory as MySQL or PHP.
However, the memory may be used by OS VM cache.

Igor Sysoev

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