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<body style="background-color: white">
-<p><a name="__index__"></a></p>
+
<!-- INDEX BEGIN -->
+<div name="index">
+<p><a name="__index__"></a></p>
<!--
<ul>
<li><a href="#name">NAME</a></li>
<li><a href="#synopsis">SYNOPSIS</a></li>
<li><a href="#description">DESCRIPTION</a></li>
- <li><a href="#aberrant_behavior_detection_with_holtwinters_forecasting">Aberrant Behavior Detection with Holt-Winters Forecasting</a></li>
+ <ul>
+
+ <li><a href="#filename"><em>filename</em></a></li>
+ <li><a href="#__start__b_start_time__default__now___10s_"><strong>-start</strong>|<strong>-b</strong> <em>start time</em> (default: now - 10s)</a></li>
+ <li><a href="#__step__s_step__default__300_seconds_"><strong>-step</strong>|<strong>-s</strong> <em>step</em> (default: 300 seconds)</a></li>
+ <li><a href="#ds_ds_name_dst_dst_arguments"><strong>DS:</strong><em>ds-name</em><strong>:</strong><em>DST</em><strong>:</strong><em>dst arguments</em></a></li>
+ <li><a href="#rra_cf_cf_arguments"><strong>RRA:</strong><em>CF</em><strong>:</strong><em>cf arguments</em></a></li>
+ </ul>
+
+ <li><a href="#aberrant_behavior_detection_with_holt_winters_forecasting">Aberrant Behavior Detection with Holt-Winters Forecasting</a></li>
<li><a href="#the_heartbeat_and_the_step">The HEARTBEAT and the STEP</a></li>
<li><a href="#how_to_measure">HOW TO MEASURE</a></li>
<li><a href="#example">EXAMPLE</a></li>
<li><a href="#example_3">EXAMPLE 3</a></li>
<li><a href="#author">AUTHOR</a></li>
</ul>
+
-->
+
+
+</div>
<!-- INDEX END -->
<p>
<p>The create function of RRDtool lets you set up new Round Robin
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>
-
-<dd>
+<p>
+</p>
+<h2><a name="filename"><em>filename</em></a></h2>
<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
+with the extension <em class="file">.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>
-
-<dd>
+<p>
+</p>
+<h2><a name="__start__b_start_time__default__now___10s_"><strong>--start</strong>|<strong>-b</strong> <em>start time</em> (default: now - 10s)</a></h2>
<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>
-
-<dd>
+<p>
+</p>
+<h2><a name="__step__s_step__default__300_seconds_"><strong>--step</strong>|<strong>-s</strong> <em>step</em> (default: 300 seconds)</a></h2>
<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>
-
-<dd>
+<p>
+</p>
+<h2><a name="ds_ds_name_dst_dst_arguments"><strong>DS:</strong><em>ds-name</em><strong>:</strong><em>DST</em><strong>:</strong><em>dst arguments</em></a></h2>
<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''
+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="gauge" class="item"><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="counter" class="item"><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="derive" class="item"><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>
-
-<dd>
+<p><strong>NOTE on COUNTER vs DERIVE</strong></p>
<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
+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 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>
+<dt><strong><a name="absolute" class="item"><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="compute" class="item"><strong>COMPUTE</strong></a></strong></dt>
<dd>
<p>is for storing the result of a formula applied to other data sources
formula. Consolidation functions are then applied normally to the PDPs
of the COMPUTE data source (that is the rpn-expression is only applied
to generate PDPs). In database software, such data sets are referred
-to as ``virtual'' or ``computed'' columns.</p>
+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>
+<p>
+</p>
+<h2><a name="rra_cf_cf_arguments"><strong>RRA:</strong><em>CF</em><strong>:</strong><em>cf arguments</em></a></h2>
<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>. The format of <strong>RRA</strong> line for these
-consolidation functions is:</p>
+<strong>MIN</strong>, <strong>MAX</strong>, <strong>LAST</strong>.</p>
+<dl>
+<dt><strong><a name="average" class="item">AVERAGE</a></strong></dt>
+
+<dd>
+<p>the average of the data points is stored.</p>
</dd>
+<dt><strong><a name="min" class="item">MIN</a></strong></dt>
+
<dd>
-<p><strong>RRA:</strong><em>AVERAGE | MIN | MAX | LAST</em><strong>:</strong><em>xff</em><strong>:</strong><em>steps</em><strong>:</strong><em>rows</em></p>
+<p>the smallest of the data points is stored.</p>
+</dd>
+<dt><strong><a name="max" class="item">MAX</a></strong></dt>
+
+<dd>
+<p>the largest of the data points is stored.</p>
</dd>
+<dt><strong><a name="last" class="item">LAST</a></strong></dt>
+
<dd>
+<p>the last data points is used.</p>
+</dd>
+</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
+<em>interesting</em> properties of your data is kept across the aggregation
+process.</p>
+<p>The format of <strong>RRA</strong> line for these
+consolidation functions is:</p>
+<p><strong>RRA:</strong><em>AVERAGE | MIN | MAX | LAST</em><strong>:</strong><em>xff</em><strong>:</strong><em>steps</em><strong>:</strong><em>rows</em></p>
<p><em>xff</em> The xfiles factor defines what part of a consolidation interval may
be made up from <em>*UNKNOWN*</em> data while the consolidated value is still
regarded as known. It is given as the ratio of allowed <em>*UNKNOWN*</em> PDPs
to the number of PDPs in the interval. Thus, it ranges from 0 to 1 (exclusive).</p>
-</dd>
-<dd>
<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>
-</dd>
-<dd>
-<p><em>rows</em> defines how many generations of data values are kept in an <strong>RRA</strong>.</p>
-</dd>
-</li>
-</dl>
+<p><em>rows</em> defines how many generations of data values are kept in an <strong>RRA</strong>.
+Obviously, this has to be greater than zero.</p>
<p>
</p>
<hr />
-<h1><a name="aberrant_behavior_detection_with_holtwinters_forecasting">Aberrant Behavior Detection with Holt-Winters Forecasting</a></h1>
+<h1><a name="aberrant_behavior_detection_with_holt_winters_forecasting">Aberrant Behavior Detection with Holt-Winters Forecasting</a></h1>
<p>In addition to the aggregate functions, there are a set of specialized
functions that enable <strong>RRDtool</strong> to provide data smoothing (via the
Holt-Winters forecasting algorithm), confidence bands, and the
<p><strong>RRA:</strong><em>HWPREDICT</em><strong>:</strong><em>rows</em><strong>:</strong><em>alpha</em><strong>:</strong><em>beta</em><strong>:</strong><em>seasonal period</em>[<strong>:</strong><em>rra-num</em>]</p>
</li>
<li>
-<p><strong>RRA:</strong><em>SEASONAL</em><strong>:</strong><em>seasonal period</em><strong>:</strong><em>gamma</em><strong>:</strong><em>rra-num</em></p>
+<p><strong>RRA:</strong><em>MHWPREDICT</em><strong>:</strong><em>rows</em><strong>:</strong><em>alpha</em><strong>:</strong><em>beta</em><strong>:</strong><em>seasonal period</em>[<strong>:</strong><em>rra-num</em>]</p>
</li>
<li>
-<p><strong>RRA:</strong><em>DEVSEASONAL</em><strong>:</strong><em>seasonal period</em><strong>:</strong><em>gamma</em><strong>:</strong><em>rra-num</em></p>
+<p><strong>RRA:</strong><em>SEASONAL</em><strong>:</strong><em>seasonal period</em><strong>:</strong><em>gamma</em><strong>:</strong><em>rra-num</em>[<strong>:smoothing-window=</strong><em>fraction</em>]</p>
+</li>
+<li>
+<p><strong>RRA:</strong><em>DEVSEASONAL</em><strong>:</strong><em>seasonal period</em><strong>:</strong><em>gamma</em><strong>:</strong><em>rra-num</em>[<strong>:smoothing-window=</strong><em>fraction</em>]</p>
</li>
<li>
<p><strong>RRA:</strong><em>DEVPREDICT</em><strong>:</strong><em>rows</em><strong>:</strong><em>rra-num</em></p>
<p>These <strong>RRAs</strong> differ from the true consolidation functions in several ways.
First, each of the <strong>RRA</strong>s is updated once for every primary data point.
Second, these <strong>RRAs</strong> are interdependent. To generate real-time confidence
-bounds, a matched set of HWPREDICT, SEASONAL, DEVSEASONAL, and
-DEVPREDICT must exist. Generating smoothed values of the primary data points
-requires both a HWPREDICT <strong>RRA</strong> and SEASONAL <strong>RRA</strong>. Aberrant behavior
-detection requires FAILURES, HWPREDICT, DEVSEASONAL, and SEASONAL.</p>
-<p>The actual predicted, or smoothed, values are stored in the HWPREDICT
-<strong>RRA</strong>. The predicted deviations are stored in DEVPREDICT (think a standard
-deviation which can be scaled to yield a confidence band). The FAILURES
-<strong>RRA</strong> stores binary indicators. A 1 marks the indexed observation as
-failure; that is, the number of confidence bounds violations in the
-preceding window of observations met or exceeded a specified threshold. An
-example of using these <strong>RRAs</strong> to graph confidence bounds and failures
-appears in <a href="././rrdgraph.html">the rrdgraph manpage</a>.</p>
+bounds, a matched set of SEASONAL, DEVSEASONAL, DEVPREDICT, and either
+HWPREDICT or MHWPREDICT must exist. Generating smoothed values of the primary
+data points requires a SEASONAL <strong>RRA</strong> and either an HWPREDICT or MHWPREDICT
+<strong>RRA</strong>. Aberrant behavior detection requires FAILURES, DEVSEASONAL, SEASONAL,
+and either HWPREDICT or MHWPREDICT.</p>
+<p>The predicted, or smoothed, values are stored in the HWPREDICT or MHWPREDICT
+<strong>RRA</strong>. HWPREDICT and MHWPREDICT are actually two variations on the
+Holt-Winters method. They are interchangeable. Both attempt to decompose data
+into three components: a baseline, a trend, and a seasonal coefficient.
+HWPREDICT adds its seasonal coefficient to the baseline to form a prediction, whereas
+MHWPREDICT multiplies its seasonal coefficient by the baseline to form a
+prediction. The difference is noticeable when the baseline changes
+significantly in the course of a season; HWPREDICT will predict the seasonality
+to stay constant as the baseline changes, but MHWPREDICT will predict the
+seasonality to grow or shrink in proportion to the baseline. The proper choice
+of method depends on the thing being modeled. For simplicity, the rest of this
+discussion will refer to HWPREDICT, but MHWPREDICT may be substituted in its
+place.</p>
+<p>The predicted deviations are stored in DEVPREDICT (think a standard deviation
+which can be scaled to yield a confidence band). The FAILURES <strong>RRA</strong> stores
+binary indicators. A 1 marks the indexed observation as failure; that is, the
+number of confidence bounds violations in the preceding window of observations
+met or exceeded a specified threshold. An example of using these <strong>RRAs</strong> to graph
+confidence bounds and failures appears in <a href="././rrdgraph.html">the rrdgraph manpage</a>.</p>
<p>The SEASONAL and DEVSEASONAL <strong>RRAs</strong> store the seasonal coefficients for the
Holt-Winters forecasting algorithm and the seasonal deviations, respectively.
There is one entry per observation time point in the seasonal cycle. For
<p>If SEASONAL and DEVSEASONAL <strong>RRAs</strong> are created explicitly, <em>gamma</em> need not
be the same for both. Note that <em>gamma</em> can also be changed via the
<strong>RRDtool</strong> <em>tune</em> command.</p>
+<p><em>smoothing-window</em> specifies the fraction of a season that should be
+averaged around each point. By default, the value of <em>smoothing-window</em> is
+0.05, which means each value in SEASONAL and DEVSEASONAL will be occasionally
+replaced by averaging it with its (<em>seasonal period</em>*0.05) nearest neighbors.
+Setting <em>smoothing-window</em> to zero will disable the running-average smoother
+altogether.</p>
<p><em>rra-num</em> provides the links between related <strong>RRAs</strong>. If HWPREDICT is
specified alone and the other <strong>RRAs</strong> are created implicitly, then
there is no need to worry about this argument. If <strong>RRAs</strong> are created
<p>Here is an explanation by Don Baarda on the inner workings of RRDtool.
It may help you to sort out why all this *UNKNOWN* data is popping
up in your databases:</p>
-<p>RRDtool gets fed samples at arbitrary times. From these it builds Primary
-Data Points (PDPs) at exact times on every ``step'' interval. The PDPs are
-then accumulated into RRAs.</p>
-<p>The ``heartbeat'' defines the maximum acceptable interval between
-samples. If the interval between samples is less than ``heartbeat'',
+<p>RRDtool gets fed samples/updates at arbitrary times. From these it builds Primary
+Data Points (PDPs) on every "step" interval. The PDPs are
+then accumulated into the RRAs.</p>
+<p>The "heartbeat" defines the maximum acceptable interval between
+samples/updates. If the interval between samples is less than "heartbeat",
then an average rate is calculated and applied for that interval. If
-the interval between samples is longer than ``heartbeat'', then that
-entire interval is considered ``unknown''. Note that there are other
-things that can make a sample interval ``unknown'', such as the rate
-exceeding limits, or even an ``unknown'' input sample.</p>
-<p>The known rates during a PDP's ``step'' interval are used to calculate
-an average rate for that PDP. Also, if the total ``unknown'' time during
-the ``step'' interval exceeds the ``heartbeat'', the entire PDP is marked
-as ``unknown''. This means that a mixture of known and ``unknown'' sample
-times in a single PDP ``step'' may or may not add up to enough ``unknown''
-time to exceed ``heartbeat'' and hence mark the whole PDP ``unknown''. So
-``heartbeat'' is not only the maximum acceptable interval between
-samples, but also the maximum acceptable amount of ``unknown'' time per
-PDP (obviously this is only significant if you have ``heartbeat'' less
-than ``step'').</p>
-<p>The ``heartbeat'' can be short (unusual) or long (typical) relative to
-the ``step'' interval between PDPs. A short ``heartbeat'' means you
+the interval between samples is longer than "heartbeat", then that
+entire interval is considered "unknown". Note that there are other
+things that can make a sample interval "unknown", such as the rate
+exceeding limits, or a sample that was explicitly marked as unknown.</p>
+<p>The known rates during a PDP's "step" interval are used to calculate
+an average rate for that PDP. If the total "unknown" time accounts for
+more than <strong>half</strong> the "step", the entire PDP is marked
+as "unknown". This means that a mixture of known and "unknown" sample
+times in a single PDP "step" may or may not add up to enough "known"
+time to warrent for a known PDP.</p>
+<p>The "heartbeat" can be short (unusual) or long (typical) relative to
+the "step" interval between PDPs. A short "heartbeat" means you
require multiple samples per PDP, and if you don't get them mark the
-PDP unknown. A long heartbeat can span multiple ``steps'', which means
+PDP unknown. A long heartbeat can span multiple "steps", which means
it is acceptable to have multiple PDPs calculated from a single
-sample. An extreme example of this might be a ``step'' of 5 minutes and a
-``heartbeat'' of one day, in which case a single sample every day will
+sample. An extreme example of this might be a "step" of 5 minutes and a
+"heartbeat" of one day, in which case a single sample every day will
result in all the PDPs for that entire day period being set to the
same average rate. <em>-- Don Baarda <<a href="mailto:don.baarda@baesystems.com">don.baarda@baesystems.com</a>></em></p>
<pre>
@@ -428,7 +437,7 @@ same average rate. <em>-- Don Baarda <<a href="mailto:don.baarda@baesystems.c
u|15|/ "swt" expired
u|16|
|17|----* sample4, restart "hb", create "pdp" for step1 =
- |18| / = unknown due to 10 "u" labled secs > "hb"
+ |18| / = unknown due to 10 "u" labled secs > 0.5 * step
|19| /
|20| /
|21|----* sample5, restart "hb"
@@ -450,7 +459,7 @@ 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="temperature" class="item">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="mail_messages" class="item">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="it_s_always_a_rate" class="item">It's always a Rate</a></strong></dt>
<dd>
<p>RRDtool stores rates in amount/second for COUNTER, DERIVE and ABSOLUTE
amount/second which you might be tempted to convert to an absolute
amount by multiplying by the delta-time between the points. RRDtool
plots continuous data, and as such is not appropriate for plotting
-absolute amounts as for example ``total bytes'' sent and received in a
+absolute amounts as for example "total bytes" sent and received in a
router. What you probably want is plot rates that you can scale to
bytes/hour, for example, or plot absolute amounts with another tool
that draws bar-plots, where the delta-time is clear on the plot for
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>
RRA:MIN:0.5:12:2400 \
RRA:MAX:0.5:12:2400 \
RRA:AVERAGE:0.5:12:2400</pre>
-<p>This sets up an <strong>RRD</strong> called <em>temperature.rrd</em> which accepts one
+<p>This sets up an <strong>RRD</strong> called <em class="file">temperature.rrd</em> which accepts one
temperature value every 300 seconds. If no new data is supplied for
more than 600 seconds, the temperature becomes <em>*UNKNOWN*</em>. The
minimum acceptable value is -273 and the maximum is 5'000.</p>