Monitoring A/B PDU Load with Zenoss

Redundant power is a necessity for any highly available system. Most servers have redundant power supplies and the common design pattern is to have each power supply plugged into a power distribution units that are on separate circuits. One challenge with this type of dealing with this type of design is monitoring the power load.

Monitoring A/B power is not as easy as monitoring the individual PDUs. Some servers will draw power from both power supplies, other will draw from one or the other. That being the case the circuits are almost never all or nothing, and they are almost never perfectly balanced. In order to effectively monitor the whole picture you need to monitor the aggregate power consumption of both circuits.

I’ve not really seen direct support in any Network Monitoring System that I have ever looked at. Zenoss is the NMS I have been using recently and while it has many rules for alerting it does not support alerts based on multiple data points. To solve my issue I ended up writing a small script that would query the SNMP OID for the total power load on a single PDU for two specified hosts and return the aggregate as well as the individual PDU loads in Nagios plugin format. That gave me a single data point that I could use for thresholds and alerts.

I have created a ZenPack that includes the script as well as the templates for graphing and thresholds. The thresholds and graphs are specific to a 20A circuit but could easily be modified for others.

The aggregateAPCpduAB ZenPack can be found on my github profile.


  • Looks like something other users might find interesting, email me if you want to get it posted on the list of Community ZenPacks at

    Matt Ray
    Zenoss Community Mananger

  • Having it on the community site would be great, and an honour!

  • Matt Mac OS X Google Chrome 5.0.375.70 wrote:

    Why not monitor the UPS and power port? We have a setup were we monitor each circuit outlet and alarm based on load.

  • ures Windows Vista Safari 3.1.1 wrote:

    and as for me I use ProteMac NetMine ( for network monitoring

  • @Matt,
    this is clearly a workaround for a limitation in Zenoss.
    Although it’s nice that Nick did this, I don’t think this approach should be generally recommended.
    It would IMHO be *much* better if Zenoss would just support alerting rules based on multiple datapoints.


  • Indeed, it would be much better to be able to alert on multiple datapoints (and alert on an equation containing multiple data points). IIRC Zabbix allows this but its been a while since I have looked at it.

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