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Subject: Re: [PHP-DEV] PHP causing high number of NFS getattr operations?
From: Terry@ellisons.org.uk (Terry Ellison)

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On 20/02/13 23:52, Brendon Colby wrote:
> Terry,
>
> Thanks for your detailed input. This is essentially what I did in my test setup.
>
> APC is definitely critical to the performance of our site. I'm just
> very curious to see how much impact the high number of getattr
> operations coming from the Apache/PHP servers is having on the filer.
> It looks like we might be able to move our PHP files to local storage
> to at least measure the impact this is having.
>
> Brendon
>
Brendon,

I think that PHP is a great platform; it's just that PHP's sweet spot is 
just a little off the optimum for typical scalable enterprise 
infrastructures.  IMO, the main issue that you should consider and 
discuss with your infrastructure support team is how to mitigate the 
impacts for such high-throughput business critical applications. As you 
(and Rasmus previously, IIRC) mention one key issue is what is on local 
and what is on network attached storage.

On one system that I got hauled in to troubleshoot, it turned out that 
the main problem was that the PHP session data was being written to a 
directory in shared storage, causing write-though overload that ended up 
hitting half a dozen key apps.  It was a trivial configuration change to 
move it to local storage transforming performance.  (I apologise if I am 
telling how "to suck eggs" but this is really for others tracking this 
thread) the main issue here is that the file hierarchies that must have 
some integrity over the application tier need to be on the NAS, 
everything else is a matter of convenience vs performance, so for 
example having a cron job to rsync the apps PHP hierarchy onto local 
storage might well transform your app performance and give an indirect 
boost to cohosted apps.  Happy hunting :)

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