Zimbra 5 memory usage tweaking

We support several small installations of Zimbra (less than 20 users) along with a couple of larger installations. Everyone loves the features that it provides and the price tag for the ZCS edition. In the past six months we've upgraded several clients from Zimbra 4 to Zimbra 5. In most of the cases, the driving factor was support for Firefox 3 and/or Safari 3.

One thing that has come up in the small Zimbra upgrades is a big increase in memory usage with the default settings. The default Zimbra settings are appropriate for installations supporting a couple of hundred users, but are overkill for for small user bases. Below is a set of the steps that we've taken with the small installations:

* Reduce the amount of memory that the Java mailbox process and the MySQL server can use. By default these are 30% and 40% respectively. We've been using 25% for both and seen no problems so far.

zmlocalconfig -e mailboxd_java_heap_memory_percent=25
zmlocalconfig -e mysql_memory_percent=25

* Reduce the number of amavisd processes that are started by default. Amavis is a mail content checker that is used by the anti-spam and anti-virus components. By default 10 processes start up, each taking up about 45 MB of memory. We've reduced this to two without seeing any ill effects.

Edit $ZIMBRA_HOME/conf/amavisd.conf.in and change this line:
$max_servers = 10;
to:
$max_servers = 2;

* If you are really strapped for memory, you can also disable anti-virus, but make sure you have some other method of virus filtering enabled first! Whether it's on a mail filtering service that sits in front of your mail server or on the desktop, you need some sort of protection.