[rrd-users] Re: numbers in the db are different from the actual ones??
ccpeters at qmail.qwest.net
Wed Nov 28 21:49:48 MET 2001
Your step is 300 seconds which means only one data point is stored every
five minutes. If you insert data between two five minute intervals, RRD
will simply interpolate and modify the five minute data points
accordingly. Inserting data points more often will not really gain you
anything so only collect and store at five minute intervals. If you
want finer granularity, use a smaller step size.
Also, counter values are stored as rates. The rates need to be
multiplied by the consolodation interval to come up with your original
So, if you are inserting data every five minutes, you will need to
multiply the fetched value by 300 seconds to get at the original value.
If you are fetching back far enough to hit consolodated data (your RRD
does not do any consolodation so you won't have to worry about this),
the interval will reflect the oldest RRA so don't hardcode the interval,
compute the time difference between any two rows instead.
Tekin Gulsen wrote:
> Hello everybody,
> I'm lost in a strange problem. I'm sure I missing something. The problem is
> that the values in the database do not match the actual increments.
> This is how I created the database: It's storing the number of database
> reads (incremental) every 5 minutes
> rrdtool create db.rrd --start `date +%s` --step 300
> When I updated the database using a script, the updated times and the values
> (9:11:42am) 1006783902:1327113
> (9:16:44am) 1006784204:1337988
> (9:21:46am) 1006784506:1353689
> (9:26:48am) 1006784808:1372517
> so the increments are; 10,875 15,701 and 18,928 respectively.
> when I graph this "dbreads" field, the values in the graph are approximately
> 34, 46 and 58
> when I did "rrdtool fetch db.rrd AVERAGE -r 300 --start 1006784204 --end
> 1006784900" the values were;
> 3.4002769356e+01, 4.6343752759e+01, 5.8749380652e+01 for these 3 intervals.
> Why are the values in the database (34,46,58) so much different from the
> actual increments (10,875 15,701 18,928)? When a field is defined as
> "COUNTER" isn't it supposed to store the increments only?
> I'd greatly appreciate any kind of help..
> Thanks in advance
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