[rrd-users] Time Shift on Trend Graph

Chris Mason chris at netnix.org
Mon Jul 1 12:27:00 CEST 2013


I am assuming "rrdtool last" returns the actual last time because when you
add new data to the RRD, it rotates the RRD and the stuff that was
previously at the beginning interval is pushed out - to always maintain the
same length and size of an RRD - you are always adding to the end?

I am starting to conclude, after getting the feeling that I am talking to
myself, that I can't obtain the point in my RRD when I first entered data?
Would it not be the first non-unknown value in the data source and can I
obtain this easily to use this to determine the start time of my graph?


On 28 June 2013 14:45, Chris Mason <chris at netnix.org> wrote:

> Hi,
> I have been through the documentation and I can't seem to find a way for
> the graph to grow from the left instead of the right.
> So, I thought I might try and do it manually by fetching the "first" entry
> from the rrd - similar to the "last" function.
> However, as I should have expected, although last returns the last input
> into the rrd, first is returning the first entry for the RRA, not the first
> time that I inserted data.
> Is there any way to determine the first time I inserted data into the RRA
> as opposed to the start of the RRA period?
> Thanks,
> Chris
> On 25 June 2013 16:05, Chris Mason <chris at netnix.org> wrote:
>> Hi,
>> I suppose the other option, if I am unable to achieve what I wanted, is
>> to only draw the trend line from the start of the actual data.
>> I use the following logic to draw a trend line for data source "DS1":
>> CDEF:DS1Trend=DS1,POP,COUNT,DS1Slope,*,DS1Int,+,0,INF,LIMIT
>> LINE1:DS1Trend#808080::dashes';
>> Is it possible to restrict the trend line to start when my data started
>> instead of at the beginning of the graph?
>> I would assume that any value within DS1 that was before my data would be
>> classified as unknown - is my DS1Trend CDEF removing the unknowns?
>> Thanks,
>> Chris
>> On 23 June 2013 13:17, Chris Mason <chris at netnix.org> wrote:
>>> Hi,
>>> I have the following graph which displays daily maximums over a period
>>> of a year:
>>> http://netnix.org/graph.png
>>> I have added a trend line to the graph using the Least Square Lines
>>> method. I am currently shifting the graph by 3 months using the following
>>> method:
>>> -s -1y+3months -e now+3months
>>> This works fine, but I wanted to try and shift the graph so the start of
>>> the graph is at the left most point and the graph is only ever displayed in
>>> the first 9 month period. It is easy if I only ever had more than 9 months
>>> worth of data, but if I only had 3 months worth of data, then I am looking
>>> for the graph to still start from the left with only the left 3 months
>>> being used?
>>> I am looking to try and do something similar to the "Filesystem
>>> Utilization and Predicted Trends" graph in the RRDTOOL gallery where in the
>>> picture, the graph is using the left hand side and the trends go into the
>>> right hand side.
>>> Any pointers?
>>> Thanks,
>>> Chris
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