<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 11 (filtered medium)">
<style>
<!--
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:Arial;
color:windowtext;}
@page Section1
{size:595.3pt 841.9pt;
margin:70.85pt 3.0cm 70.85pt 3.0cm;}
div.Section1
{page:Section1;}
/* List Definitions */
@list l0
{mso-list-id:238752951;
mso-list-type:hybrid;
mso-list-template-ids:-323729132 135659535 135659545 135659547 135659535 135659545 135659547 135659535 135659545 135659547;}
@list l0:level1
{mso-level-tab-stop:36.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1
{mso-list-id:2140493058;
mso-list-type:hybrid;
mso-list-template-ids:-1895556508 135659521 135659521 135659547 135659535 135659545 135659547 135659535 135659545 135659547;}
@list l1:level1
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:36.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l1:level2
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:36.0pt;
mso-level-number-position:left;
margin-left:36.0pt;
text-indent:-18.0pt;
font-family:Symbol;}
@list l1:level3
{mso-level-number-format:roman-lower;
mso-level-tab-stop:108.0pt;
mso-level-number-position:right;
text-indent:-9.0pt;}
ol
{margin-bottom:0cm;}
ul
{margin-bottom:0cm;}
-->
</style>
</head>
<body lang=PT link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Hi. I’ve been using Smokeping for a while. Please
correct me if I’m wrong.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Smokeping shows a value for the Standard Deviation (SD)
on the bottom of the graphs, labeled <b><span style='font-weight:bold'>SD</span></b>.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I believe the values Smokeping shows for sd is the “<b><span
style='font-weight:bold'>SD of the AVERAGES”</span></b> and not the “<b><span
style='font-weight:bold'>AVERAGE of the SDs”</span></b>, as it should be.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I’ll explain in this example. Imagine 2 graphs:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Graph #1:<o:p></o:p></span></font></p>
<ul style='margin-top:0cm' type=disc>
<li class=MsoNormal style='mso-list:l1 level1 lfo2'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>all the medians are
around 20ms, and there’s hardly any smoke.<o:p></o:p></span></font></li>
</ul>
<p class=MsoNormal style='margin-left:108.0pt;text-indent:-108.0pt;mso-text-indent-alt:
-9.0pt;mso-list:l1 level3 lfo2'><![if !supportLists]><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'><span style='mso-list:
Ignore'><font size=1 face="Times New Roman"><span style='font:7.0pt "Times New Roman"'>
</span></font>i.<font size=1 face="Times New Roman"><span style='font:7.0pt "Times New Roman"'>
</span></font></span></span></font><![endif]><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>STD in each pool would be
very small, “<b><span style='font-weight:bold'>average of the SDs”</span></b>
would be <u>VERY SMALL</u>.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>Graph #2:<o:p></o:p></span></font></p>
<ul style='margin-top:0cm' type=disc>
<li class=MsoNormal style='mso-list:l1 level1 lfo2'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>all the medians are
around 20ms, but there is lots of smoke.<o:p></o:p></span></font></li>
</ul>
<p class=MsoNormal style='margin-left:108.0pt;text-indent:-108.0pt;mso-text-indent-alt:
-9.0pt;mso-list:l1 level3 lfo2'><![if !supportLists]><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'><span style='mso-list:
Ignore'><font size=1 face="Times New Roman"><span style='font:7.0pt "Times New Roman"'>
</span></font>i.<font size=1 face="Times New Roman"><span style='font:7.0pt "Times New Roman"'>
</span></font></span></span></font><![endif]><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>STD in each pool would be
very big, “<b><span style='font-weight:bold'>average of the SDs”</span></b>
would be <u>VERY BIG</u>.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>But the value shown in Smokeping graphs is the “<b><span
style='font-weight:bold'>SD of the AVERAGES”</span></b>, and it will be <u>VERY
SMALL IN BOTH GRAPHS</u>, because the medians are all close to 20ms!<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I would like a value for SD that could tell me
information about the “amount of smoke” in the graph, but I believe
this would only be possible it there was a datasource (ds) for SD in each RRD,
and I don’t think this is how things are being done.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I use this command to obtain an AVERAGE RTT:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>rrdtool graph CR-BT1.rrd -s -2592000 DEF:median=CR-BT1.rrd:median:AVERAGE
PRINT:median:AVERAGE:%lf |tail -1<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<ul style='margin-top:0cm' type=disc>
<li class=MsoNormal style='mso-list:l1 level1 lfo2'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>How can I get the “<b><span
style='font-weight:bold'>SD of the AVERAGEs</span></b>”?<o:p></o:p></span></font></li>
<li class=MsoNormal style='mso-list:l1 level1 lfo2'><font size=2 face=Arial><span
lang=EN-GB style='font-size:10.0pt;font-family:Arial'>How can I get the “<b><span
style='font-weight:bold'>AVERAGE of the SDs</span></b>”? (If it’s
possible… If not, how can I obtain a value that reflects the amount
of smokein a graph?)<o:p></o:p></span></font></li>
</ul>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'>I’d appreciate a lot any help you could give me!<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-GB style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
</div>
</body>
</html>