Gaps in RRD graphs

  • I'm running a new install of pfSense 2.0.2 (amd64) on a homebuilt server (Intel Xeon E3 1220, 4GB RAM, 64GB SSD/16GB swap). Since I set up the appliance a week ago, I've noticed that the RRD graphs often contain gaps in the data of arbitrary durations and at seemingly arbitrary times.

    The gaps affect the System, Traffic, Packets, Queues and QueueDrops graphs, and uniformly so (i.e. the same time periods will be blank on all graphs). Interestingly, the Quality graph is unaffected and shows no data gaps whatsoever.

    I don't believe these data gaps are related to the hardware being overutilized; the system is quite powerful and CPU usage rarely climbs over 25% (and memory usage is usually less than 5%).

    I have confirmed that the /var/db/rrd/ script is running on my system, and have checked the system log for information but have found nothing related to RRD. I also reset all RRD data earlier today and the issue persists.

    I did notice that the gaps only occur during medium/high traffic periods. We are an office of 35 people using a single cable Internet line that is 50Mbps down/5Mbps up. At night when there is little to no WAN traffic there are no gaps in the graphs. During the day WAN traffic frequently exceeds 10Mbps for extended periods, yet the parts of the graph that do contain traffic data show it in the 6-10Mbps range.

    Is it possible that traffic over 10Mbps is what is causing the gaps? Is there anything I can adjust to prevent the gaps from occurring?

    I am not familiar with how data is logged to RRD but I am curious to know more.

    For reference, here are other forum posts I've found which seem to describe similar issues with RRD graphs but do not seem directly related to my issue:

    Thanks for your help.

  • Update: This seems to have been related to some component of the hardware I was using. I migrated my config over to a dedicated appliance (a Twitter box from TranquilNet with an Atom processor, Intel NICs and a 4GB CF card) and my RRD graphs are now gap-free. I'm still not sure which component was the root of the problem, so apologies if you happen upon this thread hoping to find the culprit. If you do, post the hardware you're using and maybe we can narrow it down.

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