Time ago we added a possibility to specify History storage period to 0 on master items. That normally return huge amount of data, which is processed by dependent items and after that is not needed at all. So dropping it after pre processing saved a lot of space in our database.

If there is such Master item monitored by Proxy, which is returning huge amount of data, despite the fact that History storage period is 0, that value is written to proxy_history and sent to Zabbix server. Which first of all grows the size of proxy database without any proper reason, and most important - heavily utilizes data sender.

There is actually no good reason to send this data to Zabbix server, because only way where this data is utilized is preprocessing, but since 4.2 preprocessing is done on Proxy side.

• Dependent items must be on same host as master item, so those will also be monitored by proxy.
• Same applies for Low level discovery
• Triggers are not calculated in case of storage period 0

Only thing that suffers is Inventory collection. Inventory is populated even if History storage period is 0. But there is no good reason to populate single inventory field from master item that return huge amount of data. Instead that should be done through dependent items.