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I've decided to split our cacti install and to start I simply backed up and migrated everything to another host. Almost all of the graphs have been working fine however a few of them are stuck with NaN values in the rrdtool.
I've stepped through the logs in debug and everything is polling correctly and calling rrdtool correctly, it just isn't accepting the values.
I've traced this back to the heartbeat in the rrdfiles. We had the original poller running at 1 minute intervals while the new host will only go at 5 minutes. 10k data sources and 1 minute intervals weren't getting along.
I did switch the heartbeat in the data_templates of the affected graphs but still had to manually tune things. Manually tuning got the graphs back working.
I've switched the step setting as well, thanks for the reminder. Do you know how to update the rrd files or is that even needed? Nothing about switching the step appears on the man pages of rrdtune.
1. Unfortunately, NO changes to any data template are propagated to any existing rrd file
2. Very unfortunately, only few parameters of existing rrd files CAN be changed AFTER having created those files
This results in
1. There are SOME parameters, which, when encountering a change require existing rrd files (of this data template) to be DELETED, thus LOOSING ALL EXISTING DATA. So, be carefully when planning exact values of those parameters. The most important of those is the STEP value (this relates to Cacti polling interval)
2. All other parameter changes currently must be propagated MANUALLY to EXISTING rrd files. The command to perform such changes is "rrdtool tune".
BTB: recently, a new "RRDtweak" Utility has been posted to rrd contrib. This one seems to leverage SOME of the restrictions (e.g. deleting and adding data source items)
So I'd rather thread necro than post a new thread since this relates heavily to my current situation--
I inherited a cacti install that was running every minute. At one point after reading a lot of how-to's and everyone referencing the cron running @ 5min, I switched to a 5min run. However, in the process I started getting blank graphs and "NaN" values from rrdinfo. After seeing this thread, I decided to reset the cron to run every minute again in hopes that it would fix my blank graphs. That didn't work. Thinking that setting the cron to 5min changed some values, I went through the web gui and reset the templates -> Data templates to use a 60 step and 120 heartbeat as they were before. As of now I have not updated the rrd files themselves via rrdtool because I worry that I'll lose the data. So, to be completely clear, would changing the step value in the web front-end all the existing data or is it the update to the rrd files themselves that would cause the issue? Would it be possible to salvage the old rrd data somehow and maybe move it on to another cacti instance? Thanks in advance for any help/advice.
BRow wrote:So, to be completely clear, would changing the step value in the web front-end all the existing data or is it the update to the rrd files themselves that would cause the issue?
Neither of the two will do. You can't change the STEP after rrd file has been created. This value is used for normalization within rrd. I only did not check the last utilities that have been published to the rrd site
R.