Random Thoughs by Paul

In Zimbra 5 the RAM settings seem to be very aggressive, aimed at servers with lots of memory. If you are trying to deploy Zimbra on a smaller server you may want/need to tune those down. I don't suggest anything under 2GB of RAM for Zimbra of any size... That said you can view the two main memory settings you'll be tweaking by running the following commands as the zimbra user:

# zmlocalconfig mailboxd_java_heap_memory_percent
# zmlocalconfig mysql_memory_percent

The output of those commands should be your current memory usage settings. On small servers I have had luck with moving these down to 25%, your mileage may vary so work with these to find the sweet spot. You want to give Zimbra as much ram as you can afford so that it can cache as much as possible to improve the end user experience.

To update the settings run the following commands as zimbra:
# zmlocalconfig -e mailboxd_java_heap_memory_percent=25
# zmlocalconfig -e mysql_memory_percent=25