[rrd-users] A script to help write RRAs

[Noah Leaman]

In an attempt to think a little less, I wrote a tiny perl script to 
help me define my RRAs. Can you all just confirm that my calculations 
are correct? I am still kinda a newbie and sometimes get confused with 
the numbers but I want to be sure I am constructing my RRDs the way I 
want them since it sucks to have to re-create the RRD and lose data.

The script (I call it rra_calc.pl) takes in 3 arguments. The --step, 
number of steps, and number of rows. The output looks like this:

$ ./rra_calc.pl 300 1 288
Data Retention Timeframe:   0y   1d   0s   0s   0s (86400 secs)
Sample Resolution:          0y   0d   0s   5s   0s (300 secs)

This one uses a 10 minute (600 seconds) --step (or PDP) setting:

$ ./rra_calc.pl 600 144 1850
Data Retention Timeframe:   5y  25d   0s   0s   0s (159840000 secs)
Sample Resolution:          0y   1d   0s   0s   0s (86400 secs)

-- 
Noah

Here is the code:

#!/usr/bin/perl -w
use strict;

if(!defined($ARGV[0])) {
	print "USAGE: $0 <step_size> <no_of_steps> <no_of_rows>\n";
	exit(0);
}

my $step_size = $ARGV[0];   # --step (amount of time that defines the 
primary data points)
my $no_of_steps = $ARGV[1]; # steps (number of steps used to define a 
single archive sample)
my $rows = $ARGV[2];        # rows (number of archive samples to store)

my $sample_size_secs = $step_size * $no_of_steps;
my $sample_size = convert_to_time($sample_size_secs);
my $retention_secs = $sample_size_secs * $rows;
my $retention = convert_to_time($retention_secs);

print "Data Retention Timeframe: $retention ($retention_secs secs)\n";
print "Sample Resolution:        $sample_size ($sample_size_secs 
secs)\n\n";

sub convert_to_time {
	my $total_seconds = shift;
	my $years = sprintf("%d", $total_seconds / 31536000);
	my $days = sprintf("%d", ($total_seconds - ($years * 31536000)) / 
86400);
	my $hours = sprintf("%d", ($total_seconds - ($years * 31536000) - 
($days * 86400)) / 3600);
	my $minutes = sprintf("%d", ($total_seconds - ($years * 31536000) - 
($days * 86400) - ($hours * 3600)) / 60);
	my $seconds = sprintf("%d", $total_seconds - ($years * 31536000) - 
($days * 86400) - ($hours * 3600) - ($minutes * 60));
	my $formated_time = sprintf("%3dy %3dd %3ds %3ds %3ds", $years, $days, 
$hours, $minutes, $seconds);
	return($formated_time);
}

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