[rrd-users] rrdupdate

Alex van den Bogaerdt alex at ergens.op.het.net
Tue Dec 25 15:19:33 CET 2007

On Tue, Dec 25, 2007 at 04:49:33PM +0400, rihad wrote:

> Thanks for a thorough explanation, but as you probably guessed I simply 
> grepped for the timestamp and NaN'ned them all :)

So you didn't find all intervals which contained this particular rate,
unless by remote chance you grepped for a timestamp which happened to
be n*86400.

> Good enough for now, as the graphs changed...

So would it do if you randomized your data...

> > Make sure you understand consolidation before you edit your RRD. You need
> > to do these computations yourself, and store the results.
> I've read the RRD manpages covering the theory etc. over the past few 
> years but forgot most of it :) It's probably easier for Tobi to consider 
> implementing this Much Wanted (c) feature in rrdupdate for some MRTG 
> folks like me :) It's so much easier to open the classic MRTG logfile in 
> vi and edit it to your liking. Most people just want to get their job 
> done quickly without having to wade through the docs for a deeper 
> understanding.

Most people want correct data, not wrong data. And wrong data is what
you now have (most likely).

If such changes happen often, then consider the following procedure:

Save your updates to a file, including a timestamp (not: "N"). Make
backups regularly. For instance do so each day, saving two files:
database.rrd.2007-12-23  database.updates.2007-12-23
database.rrd.2007-12-24  database.updates.2007-12-24
database.rrd.2007-12-25  database.updates.2007-12-25

Then consider the backed up RRD as your full backup, and the saved
timestamps as incremental backups.  Now, if you need to change a value,
revert to the backed up RRD and replay your updates (except that wrong
update, of course).
edit database.updates.2007-12-23
copy database.rrd.2007-12-23 database.rrd
rrdtool - < database.updates.2007-12-23
rrdtool - < database.updates.2007-12-24
rrdtool - < database.updates.2007-12-25

If you want this or similar functionality in RRDtool, program it!
I'm sure there are programmers who would like to do that job for you.
I know Tobi would be interested, as would I. But is it important enough
for you to hire a programmer?

Alex van den Bogaerdt

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