Some tips on performance tuning systems for Horde.  This does not cover
hardware tuning or even low level system (network, filesystem, etc) 
tuning.

Linux Tuning:
* Recompile RPMS for your architecture (e.g. i586, i686, athlon, etc).
  This applies most to your Apache, PHP, IMAP, and POP3 packages.

Apache/PHP tuning
* Consider a PHP accelerator program.  See for example
  The Zend Performance Suite (http://www.zend.com/horde.php), The ionCube PHP
  Accelerator (http://www.php-accelerator.co.uk/),
  or Turck MMCache for PHP (http://turck-mmcache.sourceforge.net/).
  These accelerators speed up access by caching the compiled PHP code,
  eliminating the need to recompile the code for every single page load. THIS
  IS PROBABLY THE EASIEST WAY TO IMPROVE THE PERFORMANCE OF HORDE.
* Compile PHP with the "--enable-inline-optimization" option to generate the
  fastest possible PHP executable.
* Only load as many Apache and PHP extensions as needed (to reduce memory
  usage).
* If using SSL with a large site, consider a hardware SSL accelerator.
* Use shared memory for the Apache SSL cache if possible.
* Use of the mcrypt PHP extension should significantly increase performance
  while also increasing security.
* Disable DNS lookups in your Apache logging, or use a caching DNS server
  on the web server host.
* Enable Apache keepalives.
* Enable PHP output compression (either in php.ini or horde/config/conf.php).
* Don't run PHP session garbage collection too often if using a slow
  storage medium (like SQL). (See session.gc_probability in php.ini)
* Consider using a faster storage medium for sessions, such as a tmpfs
  or other memory based file system.  If you are sure your apache setup
  is rock solid and you don't restart it there is a mm session driver.
  However, be aware that certain Horde applications (like IMP) make heavy
  use of caching data in sessions so memory based solutions may be exhausted
  quickly, particularly if there will be more than a single user.

Sending Mail
* Generally using a local sendmail command to send mail will result in better
  peformance than using a SMTP connection.
* Some MTA servers may be faster or more efficient than others.
  Consider switching to a faster format if needed.

IMAP tuning
* Consider an IMAP proxy for more persistent connections.  Some IMAP proxies
  are up-imapproxy (http://www.imapproxy.org/), imapproxy
  (http://www.horde.org/imapproxy/), and Perdition
  (http://www.vergenet.net/linux/perdition/).
* Some IMAP servers (or IMAP mailbox store formats) perform better than 
  others.  Consider switching to a faster format if needed.

Postgresql tuning
* Do a vacuum command periodically to tune your database
* Increase shared_buffers and sort_mem memory settings.
* If web server and database is on the same unix host, use unix sockets
  instead of network connections for database access.

MySQL tuning
* If web server and database is on the same unix host, use unix sockets
  instead of network connections for database access.
* Enable mysql query cache if you have sufficient RAM.  Edit your my.cnf
  file and add the following (change the memory size to meet your needs):
  set-variable = query_cache_size=128M 

$Horde: horde/docs/PERFORMANCE,v 1.8 2003/11/18 16:31:32 ericr Exp $