[dev] Tip for high-load Horde/IMP installation

[Max Kalika]

Quoting Etienne Goyer <etienne.goyer at linuxquebec.com>:

> I would like to hear about people experience for tweaking Apache, PHP
> and Horde for such high load.  I know Horde can be quite ressource
> intensive, so every little bit will help I suppose.  In particulair, the
> various setting of php.ini are not very familiar to me so if there is
> something important to check there, I'd like to know about it.

These items aren't exactly php.ini settings but here are a few things you
should look into:

1) since you have so much memory on your sql box, it is absolutely
essential to enable mysql query cache.  It is as easy as adding

  set-variable    = query_cache_size=128M

to your my.cnf file (alter the 128M to what you see as appropriate).  If
you want to do it at run time, issule the following query:  

  SET GLOBAL query_cache_size = 128 * 1024 * 1024;

doing this brought the load average on our sql server from 9+ down to 0.


2) Install up-imapproxy (www.imapproxy.org) for imp to connect to. This
speeds up your over all mail performance enormously.


3) With all that memory, you can probably make a decent sized tmpfs
partition for the php session data.  I imagine that it will be speedier
than on disk-storage.


4) Is your storage RAID based?  Which adapter?  A coworker here has done
some very thorough benchmarks for a few adapters and their various settings
so if you want I can post the optimal configs.

--mk