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
+(or equal to) the number of seconds specified by B<CacheTimeout>.
+That check happens on new values arriwal. 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
900 seconds might be a good value, though setting this to 7200 seconds doesn't
normally do much harm either.
+Default value for this option is 10x of B<CacheTimeout>.
+If value of B<CacheFlush> less than value of B<CacheTimeout> then default value
+used too.
+
=item B<CacheTimeout> I<Seconds>
If this option is set to a value greater than zero, the C<rrdtool plugin> will