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In a server purely running Kopano Core, it is advisable to set caches to use around 80% (in total -- including MySQL) of the RAM available in your server and can be considered to be a rule-of-thumb. The other 20% should be free for system processes, other processes (like your MTA) and the web server. . (This does not take an optional webserver into account.) Whenever you set the values too high this can result in the use of swap on your server. Swapping should be avoided, but we do want to make use of the RAM available. Therefore these settings should be a healthy balance between the risk of swapping and efficient caching in memory.


  • cell cache: around 25% of total RAM size
  • object cache: 16-64 MB
  • indexed object cache: 1632-128 MB

These cache settings need to be configured in the /etc/kopano/server.cfg and details about these cache settings are described in the sections below.


Size in bytes of the cell cache. This is the main cache used in Kopano Core. It caches all data that comes into view in tables (e.g. the view of your inbox, or any other folder). In an ideal situation, all cells would be cached, so that the database does not need to be queried for data when browsing through folders, but this would require around 1.5K per message item (email, appointment task, etc) in the entire server. If you can afford it, set this value as high as possible, up to 50% of your total RAM capacity.

Object cache (cache_object_size)

This caches objects and their respective hierarchy of folders. You can calculate the size with a simple equation:calculation;

<Concurrent<concurrent users> * <max items in a folder> * 24

Default value is 5242880 (5 MB)


Indexed object cache (cache_indexedobject_size)

This cache contains unique id's of objects. You can calculate the size with a simple calculation;

<concurrent users> * 512kb