[rrd-users] Pulling data out of rrds

[Steve Shipway]

Although the RRD is being given a COUNTER, what it is storing is the Rate.
It has already done most of your work for you!

Therefore, your fetch command is returning the average Rate (in octets per
second) for that 30s time window.  Multiple by 8 and you'll have it in
bits/sec

Steve

Steve Shipway
s.shipway at auckland.ac.nz


-----Original Message-----
From: rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch
[mailto:rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch] On
Behalf Of Munroe Sollog
Sent: Tuesday, 8 April 2014 3:08 p.m.
To: rrd-users
Subject: [rrd-users] Pulling data out of rrds

I have thousands of rrds that store network traffic data.  My goal is to get
the 'current bandwidth usage' from each.  I'm taking the the last 2 entries
from:

rrdtool fetch switch_hud/data/datab/172.16.23.250-g0-1.rrd MAX --resolution
30

I'm subtracting the values and multiplying by 8 because I'm collecting
octets.   My understanding is that because the rrds are collecting a counter
from the switches subtracting the n-1 value from the nth value gets me the
total # of bits over the given time.  If I divide that by the time span I
should get bits per second.  However, my numbers are 2-3 orders of magnitude
off when I compare it to the graph and I can't figure out why.  My hope is
that there is an easier way to do what I'm trying to do.  The graph seems to
be able to do this trivially.  Included is the output from rrdtool info 

$ rrdtool info switch_hud/data/datab/172.16.41.251-g1-0-1.rrd
filename = "switch_hud/data/datab/172.16.41.251-g1-0-1.rrd"
rrd_version = "0003"
step = 30
last_update = 1396925867
header_size = 2048
ds[inbps].index = 0
ds[inbps].type = "COUNTER"
ds[inbps].minimal_heartbeat = 120
ds[inbps].min = 0.0000000000e+00
ds[inbps].max = NaN
ds[inbps].last_ds = "8910377490"
ds[inbps].value = 5.3340333333e+03
ds[inbps].unknown_sec = 0
ds[outbps].index = 1
ds[outbps].type = "COUNTER"
ds[outbps].minimal_heartbeat = 120
ds[outbps].min = 0.0000000000e+00
ds[outbps].max = NaN
ds[outbps].last_ds = "35576830451"
ds[outbps].value = 1.2401500000e+04
ds[outbps].unknown_sec = 0
rra[0].cf = "MAX"
rra[0].rows = 5760
rra[0].cur_row = 1089
rra[0].pdp_per_row = 1
rra[0].xff = 5.0000000000e-01
rra[0].cdp_prep[0].value = NaN
rra[0].cdp_prep[0].unknown_datapoints = 0 rra[0].cdp_prep[1].value = NaN
rra[0].cdp_prep[1].unknown_datapoints = 0 rra[1].cf = "MAX"
rra[1].rows = 2880
rra[1].cur_row = 2
rra[1].pdp_per_row = 12
rra[1].xff = 5.0000000000e-01
rra[1].cdp_prep[0].value = 2.9445444444e+02
rra[1].cdp_prep[0].unknown_datapoints = 0 rra[1].cdp_prep[1].value =
8.3342888889e+02 rra[1].cdp_prep[1].unknown_datapoints = 0 rra[2].cf = "MAX"
rra[2].rows = 1440
rra[2].cur_row = 217
rra[2].pdp_per_row = 48
rra[2].xff = 5.0000000000e-01
rra[2].cdp_prep[0].value = 3.2185555556e+02
rra[2].cdp_prep[0].unknown_datapoints = 0 rra[2].cdp_prep[1].value =
1.1610480460e+03 rra[2].cdp_prep[1].unknown_datapoints = 0 rra[3].cf = "MAX"
rra[3].rows = 2920
rra[3].cur_row = 2147
rra[3].pdp_per_row = 288
rra[3].xff = 5.0000000000e-01
rra[3].cdp_prep[0].value = 3.8953555556e+02
rra[3].cdp_prep[0].unknown_datapoints = 0 rra[3].cdp_prep[1].value =
1.1610480460e+03 rra[3].cdp_prep[1].unknown_datapoints = 0 rra[4].cf = "MAX"
rra[4].rows = 1040
rra[4].cur_row = 207
rra[4].pdp_per_row = 2016
rra[4].xff = 5.0000000000e-01
rra[4].cdp_prep[0].value = 5.4072455556e+03
rra[4].cdp_prep[0].unknown_datapoints = 0 rra[4].cdp_prep[1].value =
4.7447486667e+04 rra[4].cdp_prep[1].unknown_datapoints = 0

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