It would be nice to be able to drill down to the content of the Zabbix database, to see what is filling up the database, so we can make alterations to how often monitored items are stored. Like baobab is able to show disk occupation in a neat way, and is able to drill down further (http://linux.byexamples.com/wp-content/uploads/2007/04/baobab.png)
Alternative is wading through lists of items, hoping to find the item(s) responsible.