Most MDis that are in use offer different interfaces to which you can attach your volumes. Those volumes are only available on the interface they are attached to and so is their monitoring data. Why does PRTG provide a list of all volumes and not only the ones that are available on the interface that the sensor is added to?

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The MDis do have a fallback mechanism, where the volumes get moved from one interface to another if one of the interfaces encounters a problem. Some customers want to prevent "false alarms" in these cases, so they add the sensor to both interfaces and only send a notification if both sensors are "down". It is a little tricky to only get one notification if both sensors are down.

  1. you need to create 3 devices. One for every interface and one for the "combination". The devices for the interfaces are configured using the IP address of the interface; the last device is assigned any address.
  2. Sensors for all volumes are created on both devices.
  3. One Sensor Factory sensor is added on the third "combined" device for every volume (the configuration is described below)
  4. Add notifications for the sensors on the "combined" device.

Configuration for the Factory Sensors: Channel Definition:

#1:Total IOs
Max(Channel(100001,0), Channel(100002,0))
#2:Read Percentage
Max(Channel(100001,1), Channel(100002,1))
#3:Cache Hit Percentage
Max(Channel(100001,2), Channel(100002,2))
#4:Current Speed
Max(Channel(100001,3), Channel(100002,3))
#5:Maximum Speed
Max(Channel(100001,4), Channel(100002,4))
#6:Current IOs 
Max(Channel(100001,5), Channel(100002,5))
#7:Maximum IOs
Max(Channel(100001,6), Channel(100002,6))

Error Handling: Use custom Formula

Status Definition: status(100001) AND status(100002) If a sensor has no data: Calculate the factory channels and use zero as source value

100001 and 100002 are the Sensor IDs of the sensors for the same volume on the different interfaces. The new sensor will now have the same channels as the old one and it will remain "green" (UP) as long as at least one of the two base sensors is green, plus it will show the higher of the two corresponding channel values.


Jun, 2013 - Permalink