diff --git a/lib/port.pm b/lib/port.pm
index 3501036..bd69d53 100644
--- a/lib/port.pm
+++ b/lib/port.pm
@@ -36,9 +36,15 @@ sub port_init {
 
 	my $info;
 	my @ds;
+	my @rra;
 	my @tmp;
 	my $n;
 
+	my @average;
+	my @min;
+	my @max;
+	my @last;
+
 	if(-e $rrd) {
 		$info = RRDs::info($rrd);
 		for my $key (keys %$info) {
@@ -47,15 +53,30 @@ sub port_init {
 					push(@ds, substr($key, 3, index($key, ']') - 3));
 				}
 			}
+			if(index($key, 'rra[') == 0) {
+				if(index($key, '.rows') != -1) {
+					push(@rra, substr($key, 4, index($key, ']') - 4));
+				}
+			}
 		}
 		if(scalar(@ds) / 4 != $port->{max}) {
-			logger("$myself: Detected size mismatch between 'max = $port->{max}' and $rrd (" . scalar(@ds) / 4 . "). Resizing it accordingly. All historic data will be lost. Backup file created.");
+			logger("$myself: Detected size mismatch between 'max = $port->{max}' and $rrd (" . scalar(@ds) / 4 . "). Resizing it accordingly. All historical data will be lost. Backup file created.");
+			rename($rrd, "$rrd.bak");
+		}
+		if(scalar(@rra) != 12 + (4 * $config->{max_historic_years})) {
+			logger("$myself: Detected size mismatch between 'max_historic_years' (" . $config->{max_historic_years} . ") and $rrd (" . ((scalar(@rra) -12) / 4) . "). Resizing it accordingly. All historical data will be lost. Backup file created.");
 			rename($rrd, "$rrd.bak");
 		}
 	}
 
 	if(!(-e $rrd)) {
 		logger("Creating '$rrd' file.");
+		for($n = 1; $n <= $config->{max_historic_years}; $n++) {
+			push(@average, "RRA:AVERAGE:0.5:1440:" . (365 * $n));
+			push(@min, "RRA:MIN:0.5:1440:" . (365 * $n));
+			push(@max, "RRA:MAX:0.5:1440:" . (365 * $n));
+			push(@last, "RRA:LAST:0.5:1440:" . (365 * $n));
+		}
 		for($n = 0; $n < $port->{max}; $n++) {
 			push(@tmp, "DS:port" . $n . "_i_in:GAUGE:120:0:U");
 			push(@tmp, "DS:port" . $n . "_i_out:GAUGE:120:0:U");
@@ -69,19 +90,19 @@ sub port_init {
 				"RRA:AVERAGE:0.5:1:1440",
 				"RRA:AVERAGE:0.5:30:336",
 				"RRA:AVERAGE:0.5:60:744",
-				"RRA:AVERAGE:0.5:1440:365",
+				@average,
 				"RRA:MIN:0.5:1:1440",
 				"RRA:MIN:0.5:30:336",
 				"RRA:MIN:0.5:60:744",
-				"RRA:MIN:0.5:1440:365",
+				@min,
 				"RRA:MAX:0.5:1:1440",
 				"RRA:MAX:0.5:30:336",
 				"RRA:MAX:0.5:60:744",
-				"RRA:MAX:0.5:1440:365",
+				@max,
 				"RRA:LAST:0.5:1:1440",
 				"RRA:LAST:0.5:30:336",
 				"RRA:LAST:0.5:60:744",
-				"RRA:LAST:0.5:1440:365",
+				@last,
 			);
 		};
 		my $err = RRDs::error;