# [rrd-users] Getting Total Bytes from COUNTER Data Source

Chris Mason chris at noodles.org.uk
Wed Dec 28 19:17:27 CET 2011

```>>I am assuming the data that is missing at the beginning of the RRA
>>would be considered UNKNOWN and I would expect the TOTAL function to
>>ignore it?
>
> You may think that ...
> It depends on how it's calculated - the obvious calculation is average * time.
> The average function ignores unknown periods, so the average of
> unkn,1,2,3 would be 2 (6/3), not 1.5 (6/4). If you then multiply that
> by the period (4 samples in this case), it would give you 8 instead
> of 6.

It comes down to whether you want unknowns to be 0 or the average.
As you say, it comes down to what the TOTAL function does:

If I had 'U,1,2,3' then the average would be 2 but I would hope the
TOTAL function would use 3*2 to find the TOTAL.
But other people might want it to estimate the missing values using
the average - my interpretation is that if a value isn't there, then
you can't count it.

> It's an interesting debate as to which is more accurate !
>
> NB - I don't know the actual calculation that's used. I'll leave
> someone who knows the code to comment on that.

```