Re: PHP web clusters and session information

["cmarko" <user=1602@nabble.blu.org>]

 I concur with Richard that the simplest method I have found is to simply 
change session.save_path in your php.ini file to an NFS mount.  In my own 
benchmarks, under a moderate simulated web load with hosts mounted against 
the NFS share this performed much better than when trying to use a rather 
simple method of storing it in a MySQL back-end (there is of course a lot 
of room for optimization on the later which I did not consider at the time 
as was looking for simplicity).  This seemed to peak at around 6 concurrent 
web hosts against the NFS mount point, though I only had 7 physical hosts 
to play with and so don't have insight into the drop-off beyond 7.  I can 
probably dig out my project paper detailing the specs under this testing if 
you think it might be of benefit to you.   

In theory if you used iSCSI on the back-end for the shared storage with a 
clustered file system (I am thinking GFS, as I don't believe OCFS is 
designed to perform well with the way PHP stores the session files) you 
could scale this well beyond 6 hosts without suffering any performance 
degradation. 

If you have the luxury of a BigIP, then you can start to do clever things 
such as using embedded cookies to leverage sticky sessions in pinning 
someone to a specific host in the cluster, etc.  Of course the expense of 
such puts out of reach of most open source projects and hobbyists. 

Best of luck! 
Chris 

On Wed, 14 May 2008 17:46:11 -0400, ref <[hidden email]> wrote: 
>  
> we have three front end web servers that serve millions of pages a month 
> via apache2/php5, and 
> use an NFS server to hold all session information. We had to do this as 
> the 
> front end servers are behind an SNMP balanced bigIP loadbalancer. we did 
> some tests 
> first and for us it proved faster to get the flat files from NFS than to 
> get the 
> session data from a shared DB (though I must add that the NFS mounted 
> server is 
> ALSO the DB server, so it was actually a good test). 
> 
> Richard 
> 
> 
> 
> On Wed, 2008-05-14 at 11:39 -0400, [hidden email] wrote: 
>> Are there any admins/architects that have multiple web servers using PHP 
>> and are sharing sessions. 
>> 
>> I have an open source project I've been trying to get going for a while 
>> now and I'd like to solve the major issues for this type of deployment. 
>> 
> 
> 
>