[rrd-users] Re: resize my rrd's

[Alex van den Bogaerdt]

On Thu, Jul 08, 2004 at 12:00:20PM +0200, Andras Horvai wrote:
> Hi All,
> 
> I plan to resize my rrd files. Plan to raise the daily RRA (5 minutes average) from 600 rows to 17280 rows to
> have 2 months of 5 minutes average data. I read somewhere (perhaps in cacti forum) that this can cause 
> problems eg. I lost the data what 2 weeks earlier. I read a opinion that resize the rrds more than one step.
> My question is what steps do you recommend? eg. first raise from 600 rows to 800 rows and wait 1 day (or less)
> and after raise from 800 rows to 1000 rows etc. Can you advise?

This depends on what you want and what you need.  The "problem" is
in auto-selecting the correct RRA.

If you ask for "--start end-5d --end now", RRDtool currently has no
other choice than to use the 2-hour RRA.

Next you are adding more rows to the 5-minute RRA.

RRDtool may use the 5-minute RRA where it used to use the 2-hour RRA.
Since this data is not yet known (you will be adding "NaN" rows) the
data _seems_ lost.

If your front end is careful and sets both "--start" and "--end" to
suitable values, RRDtool will select the 2-hour RRA (or even the
1-day RRA) in stead of the 5-minute RRA and no harm is done.

HTH
Alex
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