[rrd-developers] Re: Min Max / Spikes

steve rader rader at teak.wiscnet.net
Sun Feb 6 21:19:08 MET 2000

 > I am rather new to RRD and have a question that (probably) has been asked
 > before (many times).
 > I occasionally get (unexplained) spikes in graphs when polling goes down
 > or if a router is rebooted.
 > I realize I must set thge min/max values.  what are the vales ?
 > Is it assuming full duplex ?  Is it time dependent ?
 > for example. 
 > interfaces.ifTable.ifEntry.ifDescr.40 = "Serial2/0/0/28:0"
 > interfaces.ifTable.ifEntry.ifSpeed.40 = Gauge: 1536000
 > should the max for 40 be 1536000 or (1536000 * 300) or (1536000 * 300 * 2)

I'm pretty sure you should use 192000!  [Someone please correct 
me if I'm wrong...]

Here's why: man "rrdcreate" sez "[f]or a traffic-COUNTER type
DS this would be the max [...] data-rate expected from the
device."  The SNMP ifSpeed OID is max data-rate in bits/sec.
Unfortunately, SNMP counters register bytes/sec.  So you need
to convert from bits/sec to bytes/sec (1/8 conversion factor)
so you should use 192000 (1536000/8.)

 > what about other interface types ?

Interface type doesn't matter: even with half duplex mediums,
the wire may (in theory at least) be 100% utilized going just
one way and thus the max value should be full wire speed.

- - -
systems guy

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