[rrd-users] Storing whole numbers does not appear to be correct....

Hamish Whittal hamish at QEDux.co.za
Fri Jun 22 13:40:23 MEST 2001

Hi all,

I am storing the number of calls routed through a network. A look at my
rra's shows the following:

filename = "vport_201.rrd"
rrd_version = "0001"
step = 300
last_update = 992446656
ds[ds0].type = "DERIVE"
ds[ds0].minimal_heartbeat = 1800
ds[ds0].min = 0.0000000000e+00
ds[ds0].max = 5.0000000000e+01
ds[ds0].last_ds = "197"
ds[ds0].value = 0.0000000000e+00
ds[ds0].unknown_sec = 0
ds[ds1].type = "GAUGE"
ds[ds1].minimal_heartbeat = 1800
ds[ds1].min = NaN
ds[ds1].max = NaN
ds[ds1].last_ds = "UNKN"
ds[ds1].value = 3.0732000000e+04
ds[ds1].unknown_sec = 0

Having read through the tutorial, I understand that RRD does reasampling
based upon the fact that it possibly could not get the sample at the
exact moment I wanted it....but

One cannot make half a call or a third of a call, so ds1 should not be
3073.2 calls, but rather 3073 calls or 3074 or whatever the exact
reading is at the time of sampling. The effect is that the ds1 gets
stored as the number of calls per second. I would prefer the number of
calls per 5 minute sample (but that is another issue for another mail I
guess:). At the end of every hour, I now want to report on the number of
calls over the last hour, at then end of the day, the number of calls
for the last day, etc. This calls per second thing really complicates
matters. Also, since ds0 is not being stored as the exact reading (but
rather and extrapolation), the calls per second ends up being a really
long little number like 1.8567891234e-02.
e.g. suppose when I read the variable, I get 196 calls. Then I read it
again 5 mins later and get 202 calls, even though I read it after 303
seconds, I still want 202 calls recorded for this data point. So calls
per second would be 202 - 196 / 300 = 0.02 calls per second. I can work
this back to calls per 5 minutes and know that I will get an integer,
not a float.

How do I stop this interpolation from happening and mucking with my call

Thanks in advance.

Hamish Whittal          QED Technologies                Tel: +27 21 448
hamish at QEDux.co.za                                      Fax: +27 21 448
                        `The' Linux Services Company    Cel: +27 82 803

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