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How can I monitor capacity and used disk space on a NetApp?

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The NetApp disk free sensor shows only free disk space in percent and absolute values. Additionally, I would like to retrieve and show the maximum capacity of NetApp volumes resp. of the whole NetApp storage system and compare it to the disk space that is actually used. How can I achieve this?

disk-free netapp prtg sensor-factory volume

Created on Aug 20, 2014 5:00:56 PM by  Gerald Schoch [Paessler Support]



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This article applies to PRTG Network Monitor 13 or later

Monitoring the Total Capacity of a NetApp

The SNMP NetApp Disk Free sensor monitors free space on a NetApp storage system. It shows, among others, free space in percent and bytes channels in one dedicated sensor for each selected volume, but ignores the total capacity of a disk because this value usually will not change.

Calculating the Capacity of a NetApp Volume

However, if you need the maximum capacity value, you can calculate the total disk space with the existing channels of your NetApp Disk Free sensor(s). Actually, PRTG already retrieves the total disk space value from a NetApp disk to calculate the values for the free space and bytes channels:

Channel0 “Free Space”:
100 * AvailableSpace / TotalCapacity [Percent]

Channel1 “Free Bytes”:
AvailableSpace * 1024 [Bytes]

To get the capacity of a disk, divide the free space in bytes of Channel1 by the free space in percent of Channel0. So you can calculate the total disk space Total [Bytes] with this formula: Channel1 / (Channel0 / 100)

Calculating Volume Capacity with a Sensor Factory

You can monitor the maximum capacity of one NetApp disk by adding the formula to a Sensor Factory sensor:

  • Add a Sensor Factory to your PRTG installation and give it a suitable name, e.g., NetApp Capacity.
  • In the Channel Definition field, enter the formula from above. You need the following information:
    • The ID of the NetApp Disk Free sensor whose total capacity you want to calculate. You find it in the page header bar of the sensor.
    • The IDs of the channels Free Space and Free Bytes. Usually, these IDs are 0 and 1.
    • The formula for the calculation of the total capacity. See above.
  • The channel definition looks like this (replace “sensorID” accordingly):
#1:Total [Bytes]
Channel(sensorID,1) / (Channel(sensorID,0) / 100)
  • Adjust the other settings as you need and click on Continue. The sensor will start calculating the total capacity of the defined NetApp volume.

Now you calculate the capacity of one NetApp disk. Of course, you can adjust the formula to calculate the capacity of an aggregate or even of your whole NetApp storage system by adding all disks to your calculation in the channel definition.

For example, calculate the capacity of three volumes with this formula in the Sensor Factory (channel IDs are usually 0 and 1):

#1:Total Capacity [Bytes]
((channel(SensorID0,ChannelID1) / (channel(SensorID0,ChannelID0) / 100)) 
+ (channel(SensorID1,ChannelID1) / (channel(SensorID1,ChannelID0) / 100)) 
+ (channel(SensorID2,ChannelID1) / (channel(SensorID2,ChannelID0) / 100))

Comparing Capacity to Used Disk Space of a NetApp

A useful application of this maximum capacity value would be to compare it to the actually used disk space. You can add another channel to your Sensor Factory that shows disk usage in total. Create a graph for your management to see at a glance how much space is used and available on the NetApp over time!

All you need to do for this purpose is to subtract the sum of the Free Bytes channels of all NetApp Disk Free sensors from the maximum capacity of your NetApp that you calculated already before. For the three sample volumes, the formula would look like this:

#2:Total Used [Bytes]
((channel(SensorID0,ChannelID1) / (channel(SensorID0,ChannelID0) / 100)) 
+ (channel(SensorID1,ChannelID1) / (channel(SensorID1,ChannelID0) / 100)) 
+ (channel(SensorID2,ChannelID1) / (channel(SensorID2,ChannelID0) / 100)))
– (channel(SensorID0,ChannelID1) 
+ channel(SensorID1,ChannelID1) 
+ channel(SensorID2,ChannelID1))

Calculating Total Free Space in Percent for a NetApp

If you also want to see free space in percent for your whole NetApp, sum up the Free Bytes channels of your NetApp Disk Free sensors and divide this sum by the capacity of the NetApp as calculated above. For the three sample volumes from above, the formula would look like this:

#3:Total Free [Percent]
(channel(SensorID0,ChannelID1) 
+ channel(SensorID1,ChannelID1) 
+ channel(SensorID2,ChannelID1)) 
/ ((channel(SensorID0,ChannelID1) / (channel(SensorID0,ChannelID0) / 100))
+ (channel(SensorID1,ChannelID1) / (channel(SensorID1,ChannelID0) / 100)) 
+ (channel(SensorID2,ChannelID1) / (channel(SensorID2,ChannelID0) / 100)))
* 100

Capacity vs Used Disk Space at a Glance

A resulting graph for this Sensor Factory would look like this:

NetApp Capacity

The blue line shows used disk space in total compared to the capacity graph area in the background, while the pink line shows how much space is left in percent. You see immediately that used disk space approaches the capacity.


See Also

Created on Aug 20, 2014 5:16:41 PM by  Gerald Schoch [Paessler Support]

Last change on Aug 21, 2014 9:47:17 AM by  Gerald Schoch [Paessler Support]



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Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.