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Database (<strong>RRD</strong>) files. The file is created at its final, full size
and filled with <em>*UNKNOWN*</em> data.</p>
<dl>
-<dt><strong><a name="item_filename"><em>filename</em></a></strong>
+<dt><strong><a name="item_filename"><em>filename</em></a></strong></dt>
<dd>
<p>The name of the <strong>RRD</strong> you want to create. <strong>RRD</strong> files should end
with the extension <em>.rrd</em>. However, <strong>RRDtool</strong> will accept any
filename.</p>
</dd>
-</li>
-<dt><strong><a name="item_time"><strong>--start</strong>|<strong>-b</strong> <em>start time</em> (default: now - 10s)</a></strong>
+<dt><strong><a name="item_time"><strong>--start</strong>|<strong>-b</strong> <em>start time</em> (default: now - 10s)</a></strong></dt>
<dd>
<p>Specifies the time in seconds since 1970-01-01 UTC when the first
value should be added to the <strong>RRD</strong>. <strong>RRDtool</strong> will not accept
any data timed before or at the time specified.</p>
-</dd>
-<dd>
<p>See also AT-STYLE TIME SPECIFICATION section in the
<em>rrdfetch</em> documentation for other ways to specify time.</p>
</dd>
-</li>
-<dt><strong><a name="item_step"><strong>--step</strong>|<strong>-s</strong> <em>step</em> (default: 300 seconds)</a></strong>
+<dt><strong><a name="item_step"><strong>--step</strong>|<strong>-s</strong> <em>step</em> (default: 300 seconds)</a></strong></dt>
<dd>
<p>Specifies the base interval in seconds with which data will be fed
into the <strong>RRD</strong>.</p>
</dd>
-</li>
-<dt><strong><a name="item_ds_3ads_2dname_3adst_3adst_arguments"><strong>DS:</strong><em>ds-name</em><strong>:</strong><em>DST</em><strong>:</strong><em>dst arguments</em></a></strong>
+<dt><strong><a name="item_ds_3ads_2dname_3adst_3adst_arguments"><strong>DS:</strong><em>ds-name</em><strong>:</strong><em>DST</em><strong>:</strong><em>dst arguments</em></a></strong></dt>
<dd>
<p>A single <strong>RRD</strong> can accept input from several data sources (<strong>DS</strong>),
for example incoming and outgoing traffic on a specific communication
line. With the <strong>DS</strong> configuration option you must define some basic
properties of each data source you want to store in the <strong>RRD</strong>.</p>
-</dd>
-<dd>
<p><em>ds-name</em> is the name you will use to reference this particular data
source from an <strong>RRD</strong>. A <em>ds-name</em> must be 1 to 19 characters long in
the characters [a-zA-Z0-9_].</p>
-</dd>
-<dd>
<p><em>DST</em> defines the Data Source Type. The remaining arguments of a
data source entry depend on the data source type. For GAUGE, COUNTER,
DERIVE, and ABSOLUTE the format for a data source entry is:</p>
-</dd>
-<dd>
<p><strong>DS:</strong><em>ds-name</em><strong>:</strong><em>GAUGE | COUNTER | DERIVE | ABSOLUTE</em><strong>:</strong><em>heartbeat</em><strong>:</strong><em>min</em><strong>:</strong><em>max</em></p>
-</dd>
-<dd>
<p>For COMPUTE data sources, the format is:</p>
-</dd>
-<dd>
<p><strong>DS:</strong><em>ds-name</em><strong>:</strong><em>COMPUTE</em><strong>:</strong><em>rpn-expression</em></p>
-</dd>
-<dd>
<p>In order to decide which data source type to use, review the
definitions that follow. Also consult the section on ``HOW TO MEASURE''
for further insight.</p>
-</dd>
<dl>
-<dt><strong><a name="item_gauge"><strong>GAUGE</strong></a></strong>
+<dt><strong><a name="item_gauge"><strong>GAUGE</strong></a></strong></dt>
<dd>
<p>is for things like temperatures or number of people in a room or the
value of a RedHat share.</p>
</dd>
-</li>
-<dt><strong><a name="item_counter"><strong>COUNTER</strong></a></strong>
+<dt><strong><a name="item_counter"><strong>COUNTER</strong></a></strong></dt>
<dd>
<p>is for continuous incrementing counters like the ifInOctets counter in
happened at the 32bit or 64bit border and acts accordingly by adding
an appropriate value to the result.</p>
</dd>
-</li>
-<dt><strong><a name="item_derive"><strong>DERIVE</strong></a></strong>
+<dt><strong><a name="item_derive"><strong>DERIVE</strong></a></strong></dt>
<dd>
<p>will store the derivative of the line going from the last to the
room. Internally, derive works exactly like COUNTER but without
overflow checks. So if your counter does not reset at 32 or 64 bit you
might want to use DERIVE and combine it with a MIN value of 0.</p>
-</dd>
<dl>
-<dt><strong><a name="item_note_on_counter_vs_derive">NOTE on COUNTER vs DERIVE</a></strong>
+<dt><strong><a name="item_note_on_counter_vs_derive">NOTE on COUNTER vs DERIVE</a></strong></dt>
<dd>
<p>by Don Baarda <<a href="mailto:don.baarda@baesystems.com">don.baarda@baesystems.com</a>></p>
-</dd>
-<dd>
<p>If you cannot tolerate ever mistaking the occasional counter reset for a
legitimate counter wrap, and would prefer ``Unknowns'' for all legitimate
counter wraps and resets, always use DERIVE with min=0. Otherwise, using
COUNTER with a suitable max will return correct values for all legitimate
counter wraps, mark some counter resets as ``Unknown'', but can mistake some
counter resets for a legitimate counter wrap.</p>
-</dd>
-<dd>
<p>For a 5 minute step and 32-bit counter, the probability of mistaking a
counter reset for a legitimate wrap is arguably about 0.8% per 1Mbps of
maximum bandwidth. Note that this equates to 80% for 100Mbps interfaces, so
setting will eliminate the possibility of mistaking a reset for a counter
wrap.</p>
</dd>
-</li>
</dl>
-<dt><strong><a name="item_absolute"><strong>ABSOLUTE</strong></a></strong>
+</dd>
+<dt><strong><a name="item_absolute"><strong>ABSOLUTE</strong></a></strong></dt>
<dd>
<p>is for counters which get reset upon reading. This is used for fast counters
next overflow. Another usage is for things you count like number of messages
since the last update.</p>
</dd>
-</li>
-<dt><strong><a name="item_compute"><strong>COMPUTE</strong></a></strong>
+<dt><strong><a name="item_compute"><strong>COMPUTE</strong></a></strong></dt>
<dd>
<p>is for storing the result of a formula applied to other data sources
to generate PDPs). In database software, such data sets are referred
to as ``virtual'' or ``computed'' columns.</p>
</dd>
-</li>
</dl>
<p><em>heartbeat</em> defines the maximum number of seconds that may pass
between two updates of this data source before the value of the
names of data source listed previously in the create command. This is
similar to the restriction that <strong>CDEF</strong>s must refer only to <strong>DEF</strong>s
and <strong>CDEF</strong>s previously defined in the same graph command.</p>
-<dt><strong><a name="item_rra_3acf_3acf_arguments"><strong>RRA:</strong><em>CF</em><strong>:</strong><em>cf arguments</em></a></strong>
+</dd>
+<dt><strong><a name="item_rra_3acf_3acf_arguments"><strong>RRA:</strong><em>CF</em><strong>:</strong><em>cf arguments</em></a></strong></dt>
<dd>
<p>The purpose of an <strong>RRD</strong> is to store data in the round robin archives
(<strong>RRA</strong>). An archive consists of a number of data values or statistics for
each of the defined data-sources (<strong>DS</strong>) and is defined with an <strong>RRA</strong> line.</p>
-</dd>
-<dd>
<p>When data is entered into an <strong>RRD</strong>, it is first fit into time slots
of the length defined with the <strong>-s</strong> option, thus becoming a <em>primary
data point</em>.</p>
-</dd>
-<dd>
<p>The data is also processed with the consolidation function (<em>CF</em>) of
the archive. There are several consolidation functions that
consolidate primary data points via an aggregate function: <strong>AVERAGE</strong>,
<strong>MIN</strong>, <strong>MAX</strong>, <strong>LAST</strong>.</p>
-</dd>
<dl>
-<dt><strong><a name="item_average">AVERAGE</a></strong>
+<dt><strong><a name="item_average">AVERAGE</a></strong></dt>
<dd>
<p>the average of the data points is stored.</p>
</dd>
-</li>
-<dt><strong><a name="item_min">MIN</a></strong>
+<dt><strong><a name="item_min">MIN</a></strong></dt>
<dd>
<p>the smallest of the data points is stored.</p>
</dd>
-</li>
-<dt><strong><a name="item_max">MAX</a></strong>
+<dt><strong><a name="item_max">MAX</a></strong></dt>
<dd>
<p>the largest of the data points is stored.</p>
</dd>
-</li>
-<dt><strong><a name="item_last">LAST</a></strong>
+<dt><strong><a name="item_last">LAST</a></strong></dt>
<dd>
<p>the last data points is used.</p>
</dd>
-</li>
</dl>
<p>Note that data aggregation inevitably leads to loss of precision and
information. The trick is to pick the aggregate function such that the
@@ -268,6 +233,7 @@ to the number of PDPs in the interval. Thus, it ranges from 0 to 1 (exclusive).<
<p><em>steps</em> defines how many of these <em>primary data points</em> are used to build
a <em>consolidated data point</em> which then goes into the archive.</p>
<p><em>rows</em> defines how many generations of data values are kept in an <strong>RRA</strong>.</p>
+</dd>
</dl>
<p>
</p>
@@ -489,7 +455,7 @@ same average rate. <em>-- Don Baarda <<a href="mailto:don.baarda@baesystems.c
<h1><a name="how_to_measure">HOW TO MEASURE</a></h1>
<p>Here are a few hints on how to measure:</p>
<dl>
-<dt><strong><a name="item_temperature">Temperature</a></strong>
+<dt><strong><a name="item_temperature">Temperature</a></strong></dt>
<dd>
<p>Usually you have some type of meter you can read to get the temperature.
<strong>GAUGE</strong> data source type for this. RRDtool will then record your reading
together with the time.</p>
</dd>
-</li>
-<dt><strong><a name="item_mail_messages">Mail Messages</a></strong>
+<dt><strong><a name="item_mail_messages">Mail Messages</a></strong></dt>
<dd>
<p>Assume you have a method to count the number of messages transported by
number of seconds in a day. Because all math is run with Doubles, the
precision should be acceptable.</p>
</dd>
-</li>
-<dt><strong><a name="item_it_27s_always_a_rate">It's always a Rate</a></strong>
+<dt><strong><a name="item_it_27s_always_a_rate">It's always a Rate</a></strong></dt>
<dd>
<p>RRDtool stores rates in amount/second for COUNTER, DERIVE and ABSOLUTE
each point (such that when you read the graph you see for example GB
on the y axis, days on the x axis and one bar for each day).</p>
</dd>
-</li>
</dl>
<p>
</p>