[rrd-users] Re: Problems with multi-DS RRD that gets asynchronous-DS updates

[Alex van den Bogaerdt]

> 
> Argh, lost that bet :-)
> 
> Been thinking about it for a while. What could happen is that
> rrd writes an unknown at time=937503900, verify by dumping the database
> inbetween 937503900 and 937503901.
> 
> You are allowing updates to come once a day, however rrdtool will try
> and create a datapoint when it can (and if I'm right this time, it can).
> 
One more thing: You can allow for some unknown values when building
the RRA. Look at this:

        rrdtool create filename [--start|-b start time]
                [--step|-s step]
                [DS:ds-name:DST:heartbeat:min:max] [RRA:CF:xff:steps:rows]

You will probably have set xff to 0.5 which means that half of the
datapoints may be absent while still producing an other-than-unknown
entry in the RRA.
When sampling every 300 seconds and having an RRA which stores one
datapoint per row, there is either 0% or 100% unknown so this won't
change. However, in the "weekly" graph this unknown value should not
be there anymore. 

Regards,
Alex

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