[rrd-users] Re: Specification of RRA Boundaries

[Alex van den Bogaerdt]

On Mon, Aug 23, 2004 at 02:03:22PM -0400, Bush, Andrew G  [NY] wrote:
> Having searched the archives of both the development and user mailing
> lists I am aware that this topic has come up several times.
> >From the archives and documentation it is my understanding that RRA
> boundaries occur at multiple step sizes from UTC.

Not from UTC (well, that's not the design).  They are integer multiples
from the unix epoch.

> As such whenever trying to general daily summaries the boundaries are
> generated at midnight UTC.

Not at all.  That is a choice, your choice.

> Similarly when generating weekly values these seem to occur on a
> Wednesday (1/1/1970 was a Thursday)

Dito.  This just happens if you (let RRDtool) select an RRA with a
rowsize of 604800 seconds (7 days).

> I am unfortunately working in multiple timezones both on the collection
> side and visual display and am measuring discrete items such as fault
> calls.  
> Therefore having the boundaries in the correct place is important.

It sure is.

That is why you need to carefully design your database.  If you need
boundaries to occur on -for instance- 05:00 UTC, you have no choice
but to keep an RRA with a size of 3600 seconds per interval.

That way you can select "--end 05:00 UTC --start end-7d" (do not try
this, it is an example for the discussion).

"05:00 UTC" translates in "midnight your time". (05:00, or any other
appropriate value).

If you need to cope with both standard time and daylight saving time,
that is just another reason to have 3600 seconds per row.

Alex
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