Nagios Support Forum

How long is the default retention of graphing data and how can anticipate the space required for graphing data? (I assume that there's some formula for the number hosts/checks...)

-Kendall Chenoweth

Nagios would keep perfdata for up to 4 years with different granularity. This is defined in "/usr/local/nagios/etc/pnp/rra.cfg". I would not recommend modifying these values, though, as you can run out of disc space really fast...
If you need to "tweak" the performance settings in Nagios XI, you can go to: Admin->Performance Settings->Databases, and set how long you are going to keep various values in the databases.

I think 4 years is enough for me now. You can mark this topic/ticket closed. Thanks!