diff --git a/tutorial/lisa2011/rrd-by-example/ex/rrd-size.pl b/tutorial/lisa2011/rrd-by-example/ex/rrd-size.pl
--- /dev/null
@@ -0,0 +1,19 @@
+#!/usr/bin/perl
+sub rrd_sizer {
+ my ($ds_cnt,$rra_sz,$rra_cnt) = @_;
+ system 'rrdtool', 'create', 'sizer.rrd',
+ map({ "DS:d${_}:GAUGE:600:U:U" } 1..$ds_cnt),
+ map({ "RRA:AVERAGE:0.5:1:$rra_sz" } 1..$rra_cnt);
+ my $size = -s 'sizer.rrd';
+ printf "DSs: %1d RRA Row: %1d RRAs: %1d == %3d byte\n",
+ $ds_cnt,$rra_sz,$rra_cnt,$size;
+ return $size;
+ }
+# DSs RRAs RRA Rows
+my $base = rrd_sizer 1, 1, 1;
+my $ds = rrd_sizer 2, 1, 1;
+my $rra_sz = rrd_sizer 1, 2, 1;
+my $rra_cnt = rrd_sizer 1, 1, 2;
+printf "+1 DS: %3d byte\n",($ds - $base);
+printf "+1 RRA Row: %3d byte\n",($rra_sz - $base);
+printf "+1 RRA: %3d byte\n",($rra_cnt - $base);