[rrd-users] Questions of new user

[Simon Hobson]

Pavel Rubtsov wrote:

>Hm... Ok, but:
>
>01. 1260111600 Start period
>02. 1260111900
>03. 1260112200
>04. 1260112500
>05. 1260112800
>06. 1260113100
>07. 1260113400
>08. 1260113700
>09. 1260114000
>10. 1260114300
>11. 1260114600
>12. 1260114900
>?? 13. 1260115200 End period?
>
>Why 13 steps?

It isn't 13, it's 12 !

12. 1260111600 End of previous consolidated period.
01. 1260111900
02. 1260112200
03. 1260112500
04. 1260112800
05. 1260113100
06. 1260113400
07. 1260113700
08. 1260114000
09. 1260114300
10. 1260114600
11. 1260114900
12. 1260115200 End period

At each timestamp, you have the value for the previous interval - 
rrdtool only talks about history, it never tries to predict the 
future. So when you do the update for 1260115200, that supplies data 
for the period starting at 1260114900 and ending at 1260115200, and 
that in turn gives the data required to consolidate for the period 
starting at 1260111600 and ending at 1260115200.

I agree, it can take a little while to get your head round these 
details. The key to remember is that rrdtool only ever deals with 
rates over periods, and each timestamp in the output relates to the 
END of a period.

-- 
Simon Hobson

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