+=item B<CacheFlush> I<Seconds>
+
+When the C<rrdtool plugin> uses a cache (by setting B<CacheTimeout>, see below)
+it writes all values for a certain RRD-file if the oldest value is older than
+(or equal to) the number of seconds specified. If some RRD-file is not updated
+anymore for some reason (the computer was shut down, the network is broken,
+etc.) some values may still be in the cache. If B<CacheFlush> is set, then the
+entire cache is searched for entries older than B<CacheTimeout> seconds and
+written to disk every I<Seconds> seconds. Since this is kind of expensive and
+does nothing under normal circumstances, this value should not be too small.
+900 seconds might be a good value, though setting this to 7200 seconds doesn't
+normally do much harm either.
+