OPcache is an opcode cache for PHP. It is bundled with PHP 5.5.0 and later.
The following settings work really well with Drupal. For Ubunti 14.04 , these following file can be modified to incorporate the changes
/etc/php5/apache2/php.iniConfiguration:
Munin is a server and network monitoring tool. AWStats is a free powerful and featureful tool that generates advanced web, streaming, ftp or mail server statistics, graphically. This log analyzer works as a CGI or from command line and shows you all possible information your log contains, in few graphical web pages.
Sometimes both can result in High Server i/o due to its periodic cron tasks. Uninstalling via command line wont help as you may see cron based tasks for Munin and Awstats running in logs.