I want to use the phpmailer library. If I install the Debian or Ubuntu package it will be at
/usr/share/php/libphp-phpmailer/class.phpmailer.php /usr/share/php/libphp-phpmailer/class.pop3.php /usr/share/php/libphp-phpmailer/class.smtp.php
Why do I need to put another copy at another place for drupal?
I use an account on a shared computer for drupal website.
/usr/share/php is on a local disk and my account for drupal on NFS network shared disk, this makes a performance difference. They are hundreds of copies of drupal on theses server, so the operating system would need to put all libraries hundred of time in cache : those files cannot stay in cache for a long time. If I would use
/usr/share/php/libphp-phpmailer/class.phpmailer.php and all other websites would do the same, it would be much more easy for the operating system to use a copy in cache, it would be faster and reduce server load... and for people installing drupal that would be just a lot easier because they would not need any more to upload this library to the server, the library module would just find it!