[rrd-users] various questions on rrdcreate/rrd_create
rick.jones2 at hp.com
Thu Apr 21 00:54:51 CEST 2011
On Wed, 2011-04-20 at 23:28 +0100, Simon Hobson wrote:
> Rick Jones wrote:
> Where there is a likelyhood of the number of datasets changing then
> you are better off with separate files. An example of that would be
> monitoring disk space where you may add or remove a filesystem. In
> that case you'd probably want one file per filesystem.
> On the other hand, for an ethernet interface, I'd have combined those
> separate files into one since the set of values being logged isn't
> likely to change.
> Another factor is whether all the data values are going to be
> available at the same time. You cannot do a partial update - so you
> cannot update one dataset at one point in time, and another at a
> different time, when they are in the same RRD file. If you can
> collect all the data values at once (which would be the case with an
> ethernet interface), then it's one call to update them all rather
> than updating each separate file individually.
Thanks. I was wondering about ntop's decision there since with sflow
counter samples one either gets all of the interface counters or none of
> >Also, when creating with --no-overwrite, what happens if the second or
> >Nth create has a different value for things like step or heartbeat? Are
> >they simply ignored or does some sort of "conversion" take-place?
> If you don't overwrite the file, then nothing gets changed.
Which explains why, even when I set the primary step to 1 in ntop,
things were still at 300 since I didn't blow-away any of the RRDs.
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